REESE  LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


I 
! 

Class 

i 
i 

I   r-w-T»--iJ-Tl-iJ-T.-v-ir-if-tr-MrTi-u--ii-u-T^-u-ii-- 


PKACTICAL  IRRIGATION 

ITS   VALUE   AND    COST 

WITH    TABLES    OF    COMPARATIVE    COST,    RELATIVE 
SOIL  PRODUCTION,   RESERVOIR  DIMENSIONS 
AND  CAPACITIES,   AND  OTHER  DATA 
OF    VALUE    TO    THE    PRAC- 
TICAL FARMER 


BY 

AUG.  J.  BOWIE,  JR. 


A.  B.,  HARVARD  ;  S.  B.  MECHANICAL  ENGINEERING,  MASS.  INST.  OF 

TECHNOLOGY  ;  S.  B.  ELECTRICAL  ENGINEERING, 

MASS.  INST.  OF  TECHNOLOGY 


NEW   YORK 
McGRAW   PUBLISHING   COMPANY 

1908 


*>& 

QHTED,    190* 


COPYRI 

BY    THE 

McGKAW  PUBLISHING  COMPANY, 
NEW   YORK 


Stanhope  Jpress 

F.    H.   GILSON     COMPANY 
BOSTON.     U.S.A. 


PREFACE 


THE  prospect  of  converting  desert  land  into  a  flourishing  coun- 
try lends  to  irrigation  an  attractive  aspect.  Some  people,  carried 
away  with  the  possibilities  of  irrigation,  lose  sight  of  the  all-impor- 
tant financial  end  of  the  question,  and  make  extensive  investment 
in  apparatus  which  is  unnecessary  or  unsuited  to  the  work  to  be 
done.  Others,  from  ill-advised  ideas  of  economy,  endeavor  to  irri- 
gate their  land  without  properly  laying  out  their  plant,  and  spend 
for  labor  alone  many  times  the  cost  of  a  suitable  installation.  To 
speak  intelligently  about  irrigation,  we  must  know  the  cost  and 
the  value,  not  only  of  the  plant  as  a  whole,  but  of  the  individual 
parts  thereof.  These  are  subjects  of  primary  importance.  The 
actual  cash  outlay  necessary  for  operation  is  often  considered  as 
the  cost  of  irrigation,  without  making  any  allowance  for  interest 
or  depreciation  on  the  investment  in  the  irrigation  plant.  Thus 
we  find  the  popular  conception  that  water  obtained  from  an  artesian 
well  is  supplied  at  no  expense,  while  pumped  water,  owing  to  the 
expense  of  a  pumping  plant,  is  by  no  means  so  desirable.  The 
first  cost  of  the  well  is  entirely  lost  sight  of.  Although  it  is 
highly  desirable  to  avoid  the  expense  for  fuel  or  attendance,  still 
the  fixed  charges  on  a  deep  artesian  well,  when  the  flow  is  small, 
may  easily  make  artesian  water  more  expensive  than  water  pumped 
under  low  lift. 

Where  the  cost  of  obtaining  water  is  high,  expensive  means  of 
preventing  seepage  may  be  justified.  Where  fuel  is  high,  and  the 
plant  is  operating  under  a  high  lift,  an  efficient  high-grade  plant 
should  be  installed.  Where  fuel  is  cheap,  and  cheap  low-grade 
labor  is  available,  it  may  be  folly  to  install  a  high-grade  plant 
with  its  added  expense  and  complication.  How  shall  we  know 
how  far  to  go  and  what  kind  of  apparatus  to  install  ?  Obviously 
we  can  give  no  intelligent  answer  unless  we  know  the  cost  and 
mini'  of  the  plant  as  a  whole,  as  well  as  of  its  individual  parts. 
It  is  the  endeavor  of  the  writer  to  furnish  data  for  determining 


171.148 


iv  PREFACE. 

the  cost  and  value  of  irrigation,  and  of  the  apparatus  and  machin- 
ery which  may  be  used  therein. 

In  a  country  rich  in  natural  resources,  little  attention  is  usually 
given  to  the  economic  utilization  of  its  wealth.  It  is  difficult  for 
ideas  of  economy  to  receive  serious  consideration,  and  reckless 
waste  is  likely  to  exist  until  the  development  reaches  such  a  stage 
that  the  scarcity  of  material  makes  itself  keenly  felt.  This  is 
particularly  true  in  the  case  of  the  use  of  water  for  irrigation.  In 
arid  America  the  available  water  supply  is  sufficient  for  the  irriga- 
tion of  only  a  very  small  percentage  of  the  land  susceptible  of  irri- 
gation. Without  storage,  much  of  this  water  will  run  to  waste. 
Economic  considerations  require  the  ultimate  construction  of  large 
reservoir  systems  for  the  storage  of  this  water. 

Present  development  is  governed  by  the  present  cost;  but 
future  development  will  be  governed  by  the  value  of  the  water  in 
increased  production,  rather  than  by  the  present  cost  of  obtaining 
it.  The  problem  of  the  economic  use  of  water  is  becoming  of  con- 
stantly increasing  importance.  In  many  places  the  entire  supply 
available  is  consumed  by  present  methods  of  irrigation.  Although 
apparently  the  irrigation  limit  has  been  reached,  the  storage  of 
water,  the  prevention  of  seepage  losses,  and  the  use  of  proper 
scientific  methods  of  applying  the  water  so  as  to  prevent  to  a  large 
extent  losses  by  evaporation  will  usually  increase  greatly  the  area 
which  may  be  irrigated.  For  instance,  the  losses  of  water  by  evap- 
oration from  the  soil  which  may  be  avoided  by  proper  irrigation 
are  often  astonishingly  great.  This  is  well  brought  out  by  the 
important  investigations  conducted  by  Professor  Fortier,  Chief  of 
Irrigation  Investigations  of  the  United  States  Department  of 
Agriculture.  . 

The  subject  of  earth  reservoirs  has  been  treated  at  some  length 
as  it  is  felt  that  they  have  a  large  field  of  usefulness.  The  figures 
given  for  large  reservoirs  are  intended  rather  to  indicate  the  con- 
siderations which  should  be  used  in  their  design,  and  also  to  sug- 
gest their  practicability  or  impracticability,  as  the  case  may  be,  than 
to  be  of  use  in  individual  cases  where  the  topography  of  the  ground 
must  always  be  considered. 

Part  of  the  data  presented  in  this  book  is  the  result  of  investi- 
gations by  the  author  while  acting  as  expert  for  the  U.  S.  Depart- 
ment of  Agriculture,  and  is  summarized  from  the  following  bulletins 
published  by  the  Office  of  Experiment  Stations :  "  Irrigation  in 


PREFACE.  v 

Southern  Texas,"  published  as  separate  No.  6  of  Bulletin  No.  158, 
and  "  Irrigation  in  the  North  Atlantic  States,"  published  as  Bulle- 
tin No.  167. 

The  author  is  indebted  to  Mr.  A.  M.  Hunt  and  to  Mr.  Frank 
Adams  for  many  valuable  suggestions  in  connection  with  the  prep- 
aration of  this  book. 

AUG.  J.  BOWIE,  JR. 
SAN  FKANCISCO,  Jan.  2,  1908. 


CONTENTS 


CHAPTER  PAGE 

I.  WHAT  IRRIGATION  HAS  ACCOMPLISHED 1 

II.  UNITS  IN  USE 11 

III.  METHODS  OF  IRRIGATION  IN  USE 20 

IV.  EVAPORATION 23 

V.  ACTUAL  RESULTS  OF  IRRIGATION 34  ^ 

VI.   DIFFERENT  SOURCES  OF  WATER  SUPPLY 42 

The  Natural  Flow  of  Streams  —  Reservoirs  —  Natural  Reser- 
voirs —  Cost  of  Stored  Water  —  Value  of  Location  —  Artificial 
Reservoirs  —  Canals  as  Storage  Basins  —  Underground  Supply. 

VII.    METHODS  AND  APPLIANCES  FOR  OBTAINING  WATER       55 
Conduction  and  Distribution  of  Water  —  Calculation  of  the  Flow 
of  Water  in  Ditches —  Measurement  of  Flow  of  Water  —  Natu- 
ral Reservoirs  —  Wells. 

VIII.    WELLS 85 

Law  of  Flow  of  Wells  —  Methods  and  Cost  of  Boring  Wells. 

IX.  PUMPS  AND  PUMPING  MACHINERY 103 

X.  IRRIGATION  NEAR  BAKERSFIELD 128  ^ 

XI.  METHODS  OF  CHARGING  FOR  WATER  IRRIGATION     .  141 

XII.  ECONOMIC  LIMIT  OF  IRRIGATION 147 •- 

XIII.  EARTH  TANKS 153 

XIV.  LARGE  ARTIFICIAL  RESERVOIRS 166 

vii 


viii  CONTENTS 

CHAPTKK  PAGE 

XV.   LARGE  RESERVOIRS  FOR  THE  STORAGE  OF  ARTESIAN 

WATER 187 

XVI.    ECONOMIC  USES  OF  RESERVOIRS  AND  TANKS   ....     199 
APPENDIX  A 203 

APPENDIX  —  CIRCULAR  EMBANKMENTS 219 

Economic  Design  of  Large  Reservoirs  on  Level  Ground — on 
Sloping  Ground  —  on  Sloping  Ground,  for  Fixed  Belt  of  Rip- 
rap-lined Reservoirs  Constructed  on  Sloping  Ground,  with 
Fixed  "Width  of  Riprap  —  of  Large  Lined  Reservoirs  of  a 
Given  Capacity  —  of  Reservoirs  on  Level  Ground  for  the  Stor- 
age of  Artesian  "Well  Water  —  Cox's  Formula. 

INDEX  229 


PRACTICAL  IRRIGATION. 

CHAPTER  I. 
WHAT  IRRIGATION  HAS  ACCOMPLISHED. 

OF  all  the  varied  industries  and  means  of  producing  wealth, 
there  is  none  which  ever  has  or  probably  ever  will  compare  in 
importance  with  agriculture.  The  value  of  our  farm  products 
is  far  in  excess  of  the  value  of  those  from  any  other  source,  and 
is  of  inestimably  greater  benefit  to  the  world.  The  principal 
elements  affecting  the  growth  of  plant  life  consist  of  the  soil, 
climate,  cultivation,  and  the  amount  of  moisture  in  the  ground ; 
and  the  best  results  are  obtained  only  from  a  proper  combina- 
tion of  the  same. 

In  much  of  the  country  the  soil  and  climate  are  suitable  for  the 
growth  of  crops  of  various  kinds,  and  cultivation  is  entirely 
under  the  control  of  the  farmer,  but  the  amount  of  moisture  in 
the  ground  is  such  as  to  preclude  successful  farming,  in  areas  of 
enormous  extent,  owing  to  either  too  large  or  too  small  a  water 
supply.  The  proper  amount  of  moisture  may  be  artificially 
retained  in  the  soil  by  supplying  it  by  irrigation  or  removing  it 
by  drainage. 

The  United  States  may  be  divided  into  three  zones,  according 
to  the  annual  rainfall :  The  humid  zone,  where  the  rainfall  is  over 
30  inches  per  year;  the  semi-arid  zone,  where  the  rainfall  varies 
between  20  and  30  inches  per  year;  and  the  arid  zone,  where  the 
rainfall  is  less  than  20  inches  per  year. 

The  arid  zone  is  situated  mainly  in  the  western  half  of  the 
country,  while  the  humid  zone  lies  to  the  east;  and  intermediate 
between  them  is  the  semi-arid  or  semi-humid  zone,  as  it  is  some- 
times called,  the  line  of  demarcation  between  which  and  the 
other  zones  is  not  sharp.  This  zone  includes  in  general  North 
and  South  Dakota,  western  Nebraska,  western  Kansas,  Okla- 
homa and  the  Pan  Handle,  and  part  of  central  Texas. 

1 


2  PRACTICAL   IRRIGATION. 

Fig.  1  is  a  map  of  the  three  zones  of  the  United  States,  as  given 
in  "  Irrigation  in  the  United  States  "  by  F.  H.  Newell. 

It  is  popularly  supposed  that  the  designation  "  arid  "  implies 
that  the  land  is  largely  of  a  desert  character.  Such,  however, 
is  not  the  case,  aridity  simply  implying  that  the  land  receives  a 
comparatively  limited  supply  of  moisture,  and  does  not  have  any 
reference  to  the  nature  of  the  soil.  In  fact,  only  7  per  cent  of 
the  arid  region  is  composed  of  desert  land.  The  area  of  the  arid 
zone  consists  of  two-fifths  of  the  total  area  of  the  country,  and  on 
much  of  this  land,  farming,  without  irrigation,  is  impracticable, 
and  the  land  is  almost  worthless;  while  with  irrigation  it  can  be 


•B  humid 
%Z£semi  arid 
f"l  a  TV  a? 


Fig.  1.     U.  S.  Map.     Zones  of  Rainfall. 

made  highly  productive  and  of  great  value.  All  the  other 
elements  of  successful  farming  are  present  except  moisture,  and 
it  needs  but  the  application  of  water  to  the  land  to  transform 
the  country  from  a  wilderness  to  a  prosperous  and  productive 
property.  The  growth  in  value  due  to  irrigation  is  by  no 
means  confined  to  the  land  alone,  but  results  in  general  benefit 
to  the  country  in  the  establishment  of  prosperous  communities 
and  the  construction  of  railroads,  which  open  up  the  land  and 
carry  its  products  to  market.  The  growth  in  land  value  due 
to  irrigation  is  remarkable,  showing,  however,  that  the  real 
value  of  the  land  is  absolutely  dependent  on  the  application  of 
water  thereto.  For  example,  irrigable  land  in  Northern  Colo- 
rado along  the  Cache  Poudre  River,  sells  readily,  with  the  water 
right  attached,  for  from  $100  to  $200  per  acre,  while  adja- 
cent land,  similar  in  every  respect,  except  for  the  absence  of 
water  rights,  is  worth  only  a  few  dollars  per  acre.  The  same 
is  true  in  many  sections  in  the  west  where  the  value  of  irriga- 


WHAT    IRRIGATION    HAS    ACCOMPLISHED.  3 

tion  is  appreciated.    In  some  localities  —  notably  in  Southern 
California  —  water  rights  are  much  more  valuable. 

As  arid  land  is  usually  valuable  only  when  water  is  applied 
thereto,  it  has  been  held  by  some  of  the  leading  authorities  on 
irrigation  that  where  the  water  was  limited,  the  water  right 
should  be  inseparably  attached  to  the  land.  This  is  the  law  in 
some  states,  and  in  general  results  in  material  benefit,  serving 
to  prevent  speculation  in  water  rights,  with  its  consequent  ills. 

Irrigation  consists  in  supplying  artificially  to  the  soil  the 
moisture  needed  for  the  growth  of  plants.  All  soils  are  composed 
of  minute  grains  or  particles  between  which  are  void  spaces. 
These  voids  will  in  general  range  from  30  per  cent  to  50  per  cent 
of  the  total  volume,  depending  on  the  relative  sizes  of  grains, 
and  on  their  arrangement.  For  example,  crushed  rock  will  have 
a  certain  percentage  of  voids,  but  if  gravel  be  mixed  with  the 
rock,  so  as  not  to  increase  its  volume,  it  will  partially  fill  the 
spaces  between  the  rock,  and  the  mixture  will  have  a  much 
smaller  void  space  than  the  rock  alone.  If  this  mixture  be 
shaken,  the  rock  and  gravel  will  readjust  themselves,  settling, 
and  leaving  a  still  smaller  void  space.  If  the  entire  void  space 
in  a  soil  is  filled  with  water,  the  soil  is  said  to  be  saturated. 

The  growth  of  plants  requires  a  certain  amount  of  moisture 
in  the  soil  to  feed  the  nutriment  therefrom  to  the  roots  of  the 
plants.  Either  too  much  or  too  little  moisture  is  detrimental 
to  plant  growth,  and  efficient  irrigation  consists  in  supplying 
the  requisite  amount  of  moisture  to  the  soil.  However,  a  fairly 
wide  range  of  percentage  of  moisture  in  the  soil  will  in  general 
give  satisfactory  results.  When  the  soil  contains  about  20  per 
cent  of  saturation  water,  it  is  dry  to  all  appearances,  and  is  not 
suitable  for  plant  growth. 

According  to  Professor  Fortier,  about  60  per  cent  of  the  volume 
of  clay  soils  and  40  per  cent  of  the  volume  of  sandy  soils  are  open 
space,  while  the  loams  range  between.  The  moisture  in  soils 
may  be  regarded  as  composed  of  two  parts  —  the  hygroscopic 
moisture  which  clings  to  the  grains  and  requires  a  considerable 
amount  of  heat  to  drive  it  off,  and  the  free  moisture  which  fur- 
nishes nourishment  to  the  roots  of  plants.  About  one  pound  of 
free  moisture  per  ten  pounds  of  soil  is  required  for  a  good  plant 
growth.  This  is  an  approximation  varying  of  course  somewhat 
with  the  nature  of  the  soil  and  crop,  and  can  be  tested  in  the 


4  PRACTICAL   IRRIGATION. 

following  manner:  Take  an  average  sample  of  the  soil  between 
the  highest  and  lowest  levels  of  the  roots,  weigh  the  same,  and 
then  spread  it  out  in  a  pan  in  a  thin  layer  and  dry  it  for  a  day 
in  the  sun,  weighing  again.  The  difference  is  the  free  water. 
The  sample  taken  where  the  plants  are  growing  well  will  show 
the  proper  amount  of  moisture. 

The  moisture  required  for  plant  growth  will  vary  with  the 
condition  of  the  crop.  For  example,  crops  such  as  onions, 
strawberries,  etc.,  require  moisture,  especially  during  the  time 
the  bulbs  and  the  berries  are  maturing.  Climatic  conditions 
largely  affect  the  irrigation  requirements.  It  is  not  sufficient 
that  the  total  rainfall  be  up  to  a  certain  quantity,  but  the  dis- 
tribution thereof  should  also  be  such  as  to  insure  the  proper 
moisture  in  the  ground  during  the  growing  season.  In  many 
arid  countries  almost  the  total  supply  of  moisture  must  be 
provided  by  irrigation,  while  in  humid  countries  irrigation  is 
simply  a  protection  against  the  effect  of  a  drought.  The 
depths  of  the  roots  of  the  plants  have  a  very  important  effect 
on  the  sensitiveness  of  the  plants  to  dry  spells.  The  moisture 
in  the  soil,  except  just  after  a  rainfall  or  irrigation,  will,  within 
limits,  at  first  increase  with  the  depth,  the  surface  layers  drying 
off  first.  Deep-rooted  plants  are  not  so  sensitive  to  short 
droughts  as  plants  whose  roots  are  nearer  the  surface. 

The  moisture  applied  to  the  soil  is  disposed  of  in  three  manners. 
A  large  part  is  evaporated  from  the  surface  of  the  soil,  another 
part  drains  through  the  soil  and  runs  to  waste,  while  the  third 
part  is  useful  in  nourishing  vegetation,  in  the  formation  of  the 
crop,  and  in  providing  for  the  transpiration  losses  thereof. 

The  leaves  of  plants  are  provided  with  hundreds  of  minute 
openings  per  square  inch.  It  is  through  these  openings  that 
the  plant  receives  from  the  atmosphere  the  carbon  necessary 
for  the  growth  of  the  plant,  which  unites  with  the  sap  from 
the  effect  of  the  light  rays.  These  openings  into  the  central 
portion  of  the  leaf  furnish  passages  for  the  evaporation  of  water 
from  the  leaf.  This  is  known  as  the  transpiration  loss,  the 
moisture  being  carried  off  by  the  air. 

The  openings  into  the  leaves  close  up  automatically  when  it  is 
dark,  thus  checking  the  loss  of  moisture  which  would  otherwise 
occur.  So  nature  has  provided  plants  with  means  for  conserving 
to  the  utmost  the  supply  of  moisture  so  necessary  for  their  growth. 


WHAT   IRRIGATION    HAS   ACCOMPLISHED.  5 

Tests  by  Professor  King  have  shown  the  remarkable  fact  that 
transpiration  losses  occur  only  when  it  is  light,  and  that  when 
it  is  dark  they  practically  cease.  Also,  unlike  losses  by  evapora- 
tion, they  remain  practically  independent  of  the  amount  of 
moisture  in  the  air,  but  are  about  equal  on  wet  or  dry  days. 
The  wind,  however,  will  increase  considerably  losses  of  this  nature. 

In  climates  where  the  air  is  moist,  the  soil  evaporation  is 
greatly  reduced ;  while,  if  the  climate  is  dry  and  subject  to  winds, 
the  evaporation  will  be  greatly  increased. 

The  nature  of  the  soil  plays  an  important  part  in  the  effect  of 
irrigation.  It  is  important  in  many  soils  where  evaporation 
losses  may  be  high,  to  take  precaution  to  reduce  the  same. 
Particularly  is  this  true  of  a  soil  which  tends  to  crack  open  when 
drying  after  an  irrigation.  A  fine  protective  mulch  of  earth 
forms  the  greatest  protection  against  evaporation  losses;  and 
where  it  is  possible  to  do  so,  cultivation  as  soon  as  is  practicable 
after  irrigation  will  be  highly  beneficial  in  preventing  evapora- 
tion. It  should  be  remembered  that  irrigation  cannot  take 
the  place  of  cultivation.  Experiments  have  shown  that  when 
the  surface  is  kept  moist  for  four  days  after  water  is  turned  on, 
from  1  to  3  inches  in  depth  will  be  lost  by  evaporation.  If 
the  soil  is  saturated  this  loss  will  approximate  the  higher  figure, 
but,  if  only  moist,  it  will  be  nearer  the  lower  figure. 

Deep  soils  will  allow  the  storage  of  considerable  quantities  of 
water,  but  this  is  of  value  to  plant  growth  mainly  where  the 
roots  of  the  plants  are  also  deep.  If  the  subsoil  be  gravelly,  care 
should  be  taken  not  to  apply  water  in  such  quantities  that  a 
large  amount  may  be  lost  by  seepage  through  the  same. 

On  the  other  hand,  a  clay  subsoil,  near  the  surface,  may  hold 
the  water  so  high  that  evaporation  losses  may  be  large.  The 
depth  to  which  water  will  penetrate  will  depend  on  the  nature 
and  condition  of  the  soil  with  respect  to  dryness. 

In  general,  from  4  to  9  inches  of  water  will  be  required  to 
moisten  the  soil  to  a  depth  of  4  feet. 

The  effect  of  the  application  of  water  to  land  will  be  to  raise 
the  level  of  the  ground  water,  carrying  with  it  the  various  salts 
dissolved  from  the  soil.  This  is  brought  to  the  surface  of  the 
ground  by  capillary  action,  where  it  leaves  the  salts  when  it 
evaporates.  Should  these  salts  be  in  quantity  and  of  a  detrimen- 
tal character,  they  will  accumulate  until  they  destroy  plant  life. 


6  PRACTICAL    IRRIGATION. 

The  various  compositions  known  as  alkali  and  also  sodium 
chloride  form  the  main  sources  of  trouble.  In  land  where  the 
drainage  is  not  naturally  good,  and  where  trouble  of  this  nature 
is  likely  to  be  encountered,  it  may  be  obviated  by  installing 
artificial  drainage.  This,  however,  is  usually  quite  expensive, 
and  hence  undesirable  if  it  can  be  avoided.  Economy  in  the 
use  of  water  and  frequent  cultivation  will  be  of  great  assist- 
ance in  preventing  damage  from  injurious  salts  in  the  soil,  in 
addition  to  effecting  excellent  results  in  checking  evapora- 
tion. 

In  addition  to  possible  damage  from  the  salts  in  the  soil,  the 
rise  of  the  ground  water  may  cause  serious  damage  to  plant 
growth,  by  excessive  moisture  near  the  roots  of  the  plants.  The 
proper  drainage  of  land  is  essential  where  extensive  irrigation 
is  to  be  employed,  and  in  many  places  large  tracts  of  land  have 
been  injured  by  receiving  the  drainage  from  adjacent  irrigated 
land,  the  ground  water  rising  sufficiently  high  to  drown  out  the 
plant  growth  and  in  some  cases  to  make  a  bog  out  of  the  country. 
Before  endeavoring  to  make  extensive  irrigation  development, 
it  is  very  essential  to  see  that  the  land  is  so  situated  that  it  has 
the  advantages  of  natural  drainage,  since  otherwise  it  may  be 
necessary  to  install  an  artificial  drainage  system,  adding  greatly 
to  the  expense.  In  all  cases,  however,  economy  in  the  use  of 
water  is  doubly  beneficial  because  it  decreases  the  cost  of  irri- 
gation and  also  the  dangers  arising  from  poor  drainage.  So 
drainage  is  as  important  for  plant  growth  as  is  irrigation,  either 
an  excess  or  deficiency  of  water  resulting  injuriously.  Drainage 
prevents  the  stagnation  of  the  ground  water,  and  allows  the 
plant  roots  to  draw  from  the  air  in  the  soil  the  oxygen  neces- 
sary for  plant  growth.  Where  injurious  salts  are  present  in  the 
ground,  it  also  prevents  them,  after  they  are  dissolved,  from 
rising  and  killing  vegetation. 

Excessive  moisture  renders  the  ground  so  soft  that  it  is 
impossible  to  work  it,  so  drainage  may  be  of  a  threefold 
benefit. 

The  value  of  irrigation  depends  largely  on  the  nature  of  the 
crop  as  well  as  on  the  yield  of  unirrigated  crops.  The  general 
subject  of  values  and  costs  is  a  matter  on  which  there  is  liable 
to  be  considerable  difference  of  opinion,  even  in  the  same  case. 
It  is  endeavored  in  this  book  to  give  as  far  as  possible  a  uniform 


WHAT   IRRIGATION    HAS   ACCOMPLISHED.  7 

standard  of  determining  costs.     The  actual  cost  will  be  made  up 
of  three  parts: 

1.  Actual  cash  running  expenses. 

2.  Interest  and  taxes. 

3.  Depreciation. 

Too  frequently  is  the  actual  cash  outlay  regarded  as  the  cost, 
no  charge  being  made  for  the  other  sources  of  expense,  though 
they  may  be  often  in  excess  of  the  assumed  cost. 

The  value  of  irrigation  will  be  the  difference  between  the 
increased  value  of  the  crop  per  acre  due  to  irrigation,  and  the 
cost  of  irrigation,  included  in  which  will  be  the  cost  of  any 
additional  farming  operations  made  necessary  by  irrigation. 

As  has  been  pointed  out,  the  value  of  irrigation  is  by  no  means 
confined  to  the  actual  direct  value,  but  in  many  cases  has  greater 
indirect  results  in  the  upbuilding  of  the  country,  and  of  the 
industries  to  which  it  gives  rise. 

In  arid  countries  the  whole  crop  may  be  due  to  irrigation, 
without  which  nothing  can  be  raised. 

In  semi-arid  countries,  irrigation,  while  not  a  necessity,  may 
become  a  commercial  necessity  from  the  greatly  increased  values 
of  the  crops. 

In  humid  climates,  where  the  rainfall  is  usually  well  distributed, 
irrigation  is  of  value  only  when  the  distribution  is  uneven. 
Where  conditions  are  favorable  and  the  irrigation  development 
very  cheap,  it  will  undoubtedly  pay  to  irrigate  field  crops,  though 
expensive  development  would  preclude  such  a  thing.  In  the 
case  of  garden  truck  where  the  values  of  crops  are  very  large, 
irrigation,  even  though  very  expensive,  will  pay  for  itself  many 
times  over.  Crops  of  this  nature  are  more  sensitive  to  moisture 
requirements  than  more  deep-rooted  crops,  and  frequently  a 
drought  of  a  few  weeks  may  result  in  the  total  failure  of  the  crop. 
The  increased  yield  of  irrigated  crops  and  the  finer  product  often 
pay  for  themselves  even  in  good  years.  Irrigation  will  also 
make  the  crop  mature  earlier  when  better  prices  may  be  obtained, 
and  will  frequently  allow  the  growth  of  one  crop  per  season 
more  than  can  be  grown  on  unirrigated  land. 

However,  the  actual  area  irrigated  .  in  humid  climates  is 
exceedingly  small  as  compared  with  arid  and  semi-arid  climates, 
and  is  confined  to  truck  and  also  to  meadow  irrigation  where 


8  PRACTICAL   IRRIGATION. 

the  water  from  small  brooks  is  turned  loose  over  the  land  for 
raising  meadow  grass. 

In  general  it  may  be  stated  that  valuable  crops  can  hardly 
afford  to  be  without  irrigation  in  most  climates,  while  crops 
of  small  value  can  be  successfully  irrigated  only  where  water  is 
cheap  or  where  the  climate  is  arid. 

Certain  crops  are  particularly  sensitive  to  the 'needs  of  irri- 
gation, such  as  strawberries,  which  require  moisture  especially 
during  the  three  weeks  while  the  fruit  is  maturing. 

As  an  illustration  of  the  value  of  irrigation,  the  following  figures 
are  taken  from  comparative  tests  on  irrigated  and  unirrigated 
land  at  Beeville,  Texas,  in  the  semi -arid  zone,  and  were  made  by 
Mr.  J.  K.  Robertson,  Superintendent  of  the  State  Experiment 
Station : 

Red  Bermuda  onions  planted  4.5  inches  apart  in  rows  15  inches 
between  centers. 

COST  OF  FARMING  1  ACRE  OF  NON-IRRIGATED  LAND. 

Plowing  and  harrowing $2  .00 

Laying  off  furrows,  —  labor  in  irrigation  before  planting, 

etc. 2 .00 

Transplanting  onions 9  .00 

Restirring  with  five-tooth  cultivator 2  .00 

Water  for  irrigation  before  planting  —  40,000  gals 1  .60 

Eight  cultivations 3  .60 

Hand  weeding 5  .00 

Pulling  onions  33.3  hours,  at  7.5  cents       2.50 

Trimming,  sacking  and  weighing,  100  hours  at  7.5  cents      .  7  .50 

Total      $35.20 

NOTE.  —  The  land  received  one  irrigation  before  planting. 

COST  OF  FARMING   1   ACRE  OF  IRRIGATED   LAND. 

Plowing  and  harrowing •    .    .  $2  .00 

Laying  off  furrows  and  labor  in  irrigation  before  planting  .    .  2  .00 

Restirring      2.00 

Transplanting 9.00 

Water  for  irrigation  before  planting 1  .60 

Eight  cultivations 3  .60 

Laying  off  rows  for  irrigation  after  planting 1  .50 

Four  irrigations  —  water 6.70 

Four  irrigations — labor      4.80 

Pulling,  trimming,  sacking  and  weighing  190  hours,  at  7.5 

cents  .  14  .25 


Total  .  $47.45 


WHAT    IRRIGATION    HAS   ACCOMPLISHED.  9 

Yield  of  non-irrigated  land  1 9,075  lb.,  at  2  cents       $381.50 

Profit 346.30 

Yield  of  irrigated  land  38,056  lb.,  at  2  cents       $761.12 

Profit $713.67 

NET  GAIN   BY   IRRIGATION $367  .37 

In  the  calculations  above,  no  allowance  was  made  for  the  fixed 
charges  of  the  irrigation  pumping  plant,  which  it  would  be,  of 
course,  impossible  to  figure  for  an  experiment  station.  From 
corresponding  stations,  this  would  be,  say,  about  $17,  leaving  a 
total  net  profit  of  $350  per  acre,  due  to  irrigation. 

On  the  same  farm  irrigated  cabbage  yielded  17,632  pounds 
against  6144  pounds  on  unirrigated  land.  The  cost  of  farming 
irrigated  land  was  $16.88  per  acre  against  $9.08  per  acre  for 
unirrigated  land.  At  2  cents  per  pound  this  gives  a  net  profit 
of  $222  per  acre  for  irrigated  over  unirrigated  crops,  and  approx- 
imating fixed  expenses  this  will  still  allow  $205  net  gain  due  to 
irrigation. 

The  greatest  part  of  the  irrigated  land  is  devoted  to  raising 
field  crops,  such  as  alfalfa,  wheat,  corn,  etc.,  and  crops  like  rice. 
Rice  irrigation  is,  however,  in  a  class  by  itself,  requiring,  as 
usually  practiced,  the  complete  submergence  of  the  land. 
The  values  of  these  crops  will  usually  lie  between  $20  and  $80 
per  acre  per  year. 

On  pages  37  to  40  are  given  further  data  of  the  cost  and 
value  of  irrigation  in  various  parts  of  the  country. 

Irrigation  should  effect  a  uniform  distribution  of  water  over 
the  land,  to  give  the  best  results.  However,  this  result  is  only 
approximated  by  the  various  methods  in  use.  The  cost  of 
irrigation  may  in  general  be  regarded  as  composed  of  two  parts: 

(1)  Cost  of  bringing  the  water  to  the  land  to  be  irrigated. 

(2)  Cost  of  applying  the  water  to  the  land. 

If  the  supply  of  water  is  not  limited,  the  most  efficient  irri- 
gation would  be  the  application  of  such  a  quantity  of  water 
that,  for  a  given  area,  the  net  returns  (that  is,  the  difference 
between  the  value  of  the  crop  and  the  cost  of  irrigation  plus  the 
cost  of  farming)  give  the  greatest  interest  on  the  investment. 
The  size  of  the  crop  will  in  general  increase  with  increasing 
quantities  of  water,  rapidly  at  first,  and  then  more  gradually, 
until  finally  a  maximum  is  reached,  after  which  increased 
amounts  of  water  will  be  a  detriment.  It  will  not  pay  to  irri- 


10  PRACTICAL   IRRIGATION. 

gate  up  to  the  point  where  the  greatest  crop  is  obtained,  but 
irrigation  should  stop  where  the  cost  of  additional  irrigation 
exceeds  the  increased  value  of  the  crop  resulting  therefrom. 

The  periods  between  the  application  of  irrigations  (the  irri- 
gation frequency)  will  have  an  important  effect  on  both  the 
cost  and  results.  The  advisable  frequency  of  irrigation  depends 
on  the  soil,  climate,  nature  of  the  crop,  and  method  of  irrigation. 
A  deep  soil,  retentive  of  moisture  with  deep-rooted  plants,  will 
require  less  frequent  irrigation  than  a  shallow  soil  where  the 
roots  of  the  crop  are  nearer  the  surface. 

Frequent  irrigation  has  the  effect  of  keeping  the  soil  more 
nearly  with  the  desired  amount  of  moisture.  However,  on  the 
other  hand,  the  expense  of  frequent  applications  of  water  is 
greater  than  the  expense  of  applying  the  same  total  quantity 
not  so  often.  Also  the  application  of  small  quantities  of  water 
is  apt  to  be  very  inefficient,  since  a  larger  percentage  will  be 
lost  by  evaporation  from  the  moist  surface  of  the  soil  than  would 
be  the  case  were  a  greater  depth  applied.  In  a  climate  liable 
to  sudden  and  heavy  rains  during  the  irrigation  season  it  is 
advisable  not  to  apply  the  water  in  too  great  amounts,  since  a 
rain  following  a  heavy  irrigation  might  do  considerable  damage 
from  excessive  moisture.  Hence  it  is  evident  that  the  advisable 
amount  of  water  to  apply  in  irrigation  and  the  advisable 
frequency  of  irrigation  depend  largely  on  the  cost  of  irrigation 
and  the  value  of  the  crop  as  well  as  on  many  other  considera- 
tions, and  that  in  general  it  will  not  pay  to  irrigate  sufficiently 
to  obtain  the  maximum  crop.  It  is  obvious,  therefore,  that  irri- 
gation is  far  from  an  exact  science,  and  that  it  is  natural  to 
expect  great  variations  in  both  the  quantities  of  water  applied 
and  the  frequency  of  application. 


CHAPTER  II. 
UNITS  IN  USE. 

THE  following  units  of  measurement  are  in  use  in  irrigation 
practice. 

The  quantity  of  water  applied  per  unit  of  land  is  usually 
expressed  as  the  depth  in  feet  or  inches  to  which  the  land  would 
be  covered  were  the  water  evenly  spread  over  it.  This  is 
referred  to  as  the  depth  of  irrigation. 

Volumes  of  water  are  expressed  in  cubic  feet,  gallons,  acre-feet 
and  acre-inches,  the  acre-foot  being  the  quantity  of  water  con- 
tained in  an  acre  1  foot  deep. 

The  flow  of  water  is  expressed  in  cubic  feet  per  second  (cu. 
ft.  per  sec.)  and  in  gallons  per  minute  (gal.  per  min.). 

Capacities  are  often  conveniently  expressed  in  terms  of  the 
flow  required  to  deliver  the  capacity  in  24  hours.  As  approxi- 
mations the  following  may  be  easily  remembered:  One  cu.  ft. 
per  sec.  =  450  gal.  per  min.,  and  this  flow  will  cover  an  acre 
2  feet  deep  in  24  hours.  Three  acre-feet  =  1,000,000  gallons. 

Another  unit  commonly  used  is  the  miner's  inch,  the  flow  of 
water  from  a  1-inch  square  orifice  under  4-inch  water  pressure 
above  the  center  of  the  hole.  This  is,  however,  defined  differently 
in  different,  parts  of  the  country  in  terms  of  an  actual  flow  vary- 
ing from  about  10  to  13  gal.  per  min.  It  is  now  legally  defined 
in  California  as  a  rate  of  flow  of  1.5  cu.  ft.  per  min.,  or  11.25  gal. 
per  min. 

The  term  "duty  of  water"  is  used  in  two  different  senses  —  as 
the  number  of  acres  a  given  flow  in  cu.  ft.  per  sec.  will  irrigate, 
and  as  the  annual  depth  of  water  applied  by  rain  and  irrigation 
to  the  land.  Neither  of  these  terms  by  themselves  gives  any 
information  about  the  length  of  the  irrigation  season,  or  frequency 
of  irrigation. 

The  annual  depth  of  water  (rain  and  irrigation)  applied  to  the 
land  cannot  necessarily  be  used  by  itself  as  a  criterion  of  the 
needs  of  irrigation.  Unequal  distribution  of  rainfall  may  lead 

11 


12  PRACTICAL   IRRIGATION. 

to  erroneous  conclusions  if  we  admit  such  an  assumption,  par- 
ticularly if  the  crop  requires  water  at  a  time  when  there  is  no 
rain.  In  arid  countries,  where  irrigation  water  is  far  in  excess 
of  rainfall,  this  may  be  a  matter  of  small  importance,  but  in  a 
country  of  considerable  rain  it  might  become  a  matter  of  some 
moment.  The  annual  depth  of  irrigation  tells  nothing  about 
the  length  of  the  irrigation  season,  and  hence  of  itself  furnishes 
no  measure,  except  in  a  general  way,  of  the  proportions  of  the 
plant  and  ditches  which  must  be  provided.  The  frequency 
of  irrigation  and  the  rate  of  supply  of  the  water  required  per 
irrigation,  on  the  contrary,  furnish  definite  information  as  to 
these  points. 

A  much  more  suitable  basis  upon  which  to  make  irrigation 
calculations  is  the  following:  Irrigation  plants  should  in  gen- 
eral be  figured  on  a  basis  of  supplying  water  at  a  rate  sufficient 
to  irrigate  continuously  all  the  desired  land,  provided  there  is 
no  rainfall.  This  means  that  a  certain  continuous  flow  of  water 
is  required  per  acre,  which  may  be  conveniently  reckoned  in 
gal.  per  min.  per  acre.  In  order  to  obtain  this  figure,  the  fre- 
quency of  irrigation  and  the  depth  per  irrigation  must  be  known. 
Dividing  the  gallons  per  acre  by  the  time  in  minutes  between 
irrigations,  gives  the  required  flow  in  gallons  per  minute.  This 
is  the  quantity  which  can  best  serve  as  the  basis  for  irrigation 
calculations  and  for  the  design  of  the  proper  size  of  plant. 
Multiplying  the  acreage  by  the  required  gal.  per  min.  per  acre 
gives  the  required  gal.  per  min.  of  the  plant,  should  it  be  operated 
continuously  24  hours  a  day.  To  find  the  proper  capacity 
plant  for  shorter  hours  of  operation,  divide  the  required  capacity 
given  above  by  the  percentage  of  the  day  it  is  desired  to  operate. 
To  find  the  total  quantity  of  water  which  must  be  applied  per 
year,  multiply  the  depth  per  irrigation  by  the  number  of  irriga- 
tions per  crop  if  the  weather  be  dry.  This  gives  the  total  depth 
of  irrigation.  Subtracting  from  this  the  rainfall  during  the 
irrigation  season  gives  the  approximate  depth  of  water  to  be 
furnished  by  irrigation  per  crop. 

If  the  maximum  flow  which  must  be  furnished  ran  continuously 
through  the  year,  it  would  cover  the  land  to  a  certain  depth. 
However,  the  water  for  irrigation  will  run  only  a  comparatively 
small  percentage  of  the  time,  and  will  cover  the  land  to  a  much 
less  depth.  The  ratio  of  the  depth  to  which  the  land  is  irri- 


UMTS   IN    USE.  13 

gated  to  the  depth  of  irrigation,  were  the  actual  flow  to  be  con- 
tinuous for  a  year,  is  known  as  the  irrigation  factor.  The 
irrigation  factor,  which  corresponds  to  the  annual  load-factor  in 
power  plants,  is  the  percentage  of  the  year  the  plant  runs  at 
full  load.  The  nearer  the  actual  flow  approaches  to  the  required 
flow,  the  higher  the  irrigation  factor,  provided  the  former  is 
greater  than  the  latter. 

The  method  of  calculation  outlined  applies  in  particular  to 
places  where  water  can  be  obtained,  when  required  in  a  quantity 
sufficient  for  the  irrigation  of  land.  There  are,  however,  many 
places  where  the  water  is  limited  in  quantity,  and  where,  when 
there  is  no  storage,  the  available  supply  runs  far  short  of  the 
needs  of  the  land  during  the  irrigation  season.  In  these  cases 
it  is  impossible  to  attempt  to  use  as  a  basis  of  calculation  for 
the  needs  of  the  land  for  water,  and  irrigation  is  of  necessity 
a  compromise  measure  between  what  is  most  desirable  and  what 
can  be  obtained.  Where  the  soil  is  deep  and  will  allow  the 
storage  of  water  therein,  it  is  not  uncommon  to  apply  heavy 
irrigations,  when  the  water  supply  is  available,  to  tide  over  the 
dry  weather  which  may  follow. 

There  is,  however,  such  a  large  percentage  of  cases  where 
suitable  water  supply  is  continuously  available,  that  the  plan  of 
calculation  outlined  is  of  material  assistance  in  the  proper 
design  of  plants. 

Tables  I  and  II  will  greatly  facilitate  the  calculation  of  irri- 
gation plants.  In  Table  I,  column  1  is  the  duty  of  water  in 
acres  per  cu.  ft.  per  sec.  which  indicates  the  number  of  acres  which 
a  flow  of  1  cu.  ft.  per  sec.  will  irrigate;  column  2,  the  required 
flow  of  water  in  gallons  per  minute  per  acre,  represents  the 
requirements  of  the  land  under  existing  conditions  of  water 
supply;  columns  3  to  13  inclusive  represent  Q,  the  depth  of 
irrigation  to  which  the  land  would  be  covered  were  the  flow 
provided  in  the  corresponding  line  of  column  2,  to  be  applied 
for  24  hours  per  day  for  the  number  of  days  stated  in  the  head 
of  the  appropriate  column.  The  remaining  columns  of  the 
table  indicate  the  annual  depth  of  water  for  irrigation  for  various 
irrigation  factors  given  in  the  headings  of  the  columns,  the 
figures  in  the  horizontal  lines  corresponding  to  the  appropriate 
required  flow  in  gallons  per  minute  per  acre. 

Tables  III  to  VIII  are  conversion  tables  for  various  units  of 


14  PRACTICAL  IRRIGATION. 

quantity  and  flow  used  in  irrigation  work.  In  order  to  abbre- 
viate as  much  as  possible,  these  tables  have  been  given  for  only 
the  nine  units  represented  in  the  first  column.  To  illustrate  the 
use  of  the  table,  suppose  that  it  were  desired  to  ascertain  the 
cubic  feet  per  second  flow  which  would  deliver  92  acre-feet  per 
day.  Referring  to  Table  III,  9  acre-ft.  per  day  =  4.5374  cu.  ft. 
per  sec.,  hence  90  acre-ft.  per  day  =  45.374  cu.  ft.  per  sec.,  2 
acre-ft.  per  day  =  1.0083  cu.  ft.  per  sec.  for  a  day.  Hence  92 
acre-ft.  =  46.38  cu.  ft.  per  sec.  for  a  day. 

To  illustrate  the  use  of  Tables  I  and  II,  consider  the  problem  of 
determining  the  size  of  plant  to  irrigate  200  acres  to  a  depth  of 
2.55  inches  every  12  days,the  number  of  irrigations  per  year  being 
10.  By  Table  II  this  requires  a  flow  of  4.0  gal.  per  min.  per  acre, 
or  800  gal.  per  min., and  will  cover  the  land  to  a  depth  of  2.1  ft. 
per  year,  the  irrigation  factor  being  33  per  cent.  If  the  plant 
be  run  only  half  the  day,the  required  flow  is  1600  gal.  per  min. 
and  the  irrigation  factor  16  per  cent.  Should  there  be  any 
unusual  losses  in  seepage  in  bringing  the  water  to  the  land,  the 
flow  should  be  correspondingly  increased.  The  calculations 
and  figures  as  given  above,  apply  to  one  kind  of  crop,  or  at  least 
to  a  crop  requiring  irrigation  at  one  certain  time  of  year  at  a 
certain  rate.  Provided  it  is  desired  to  irrigate  different  kinds 
of  crops  which  require  water  in  different  seasons  of  the  year, 
the  quantity  of  water  to  be  supplied  may  be  arrived  at  in  one 
of  two  ways:  either  by  making  assumption  of  average  values 
of  the  needs  of  the  crops,  or  else  by  figuring  each  one  out  inde- 
pendently. The  irrigation  capacity  which  should  be  furnished 
will,  of  course,  depend  upon  the  manner  in  which  the  respective 
demands  for  water  overlap.  For  example,  if  one  crop  requires 
water  in  the  summer  and  fall,  and  another  in  the  spring  and 
summer,  the  capacity  should,  of  course,  be  proportioned  to  the 
maximum  demand,  which  would  be  in  the  summer. 


UNITS  IN  USE. 


15 


0,8 


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Oi  iO  CO  1-1  O  O5  t^.  SO  tO  tO  ^  "tf  CO  CO  CO  CO  <N  <N  <N  1-1  .-i  -H 


CO  Oi  iO  CO  1-1  O 

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CO  -^  O  O  Tf  O  O  00  O1 


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16 


PRACTICAL  IRRIGATION. 


g 


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PQ      H 

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^rHiOcOrHClrHOOOOO-^CiiOC^CSCOrH^T^NOOO 
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(^  (N  rH  rH  rH  rH  rH 


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UNITS  IN  USE. 
TABLE  II. 


17 


6 

Duty  of  water.     Acres  per 

449 

224 

150 

112 

90 

75 

64 

56 

50 

••u.  ft.  per  sec. 

Required      flow  —  gal 

.     per 

I 

2 

3 

4 

5 

6 

7 

8 

9 

min.  per  acre 

days 

7 

0.37 

0.74 

1  .11 

1.48 

1  .86 

2.23 

2.60 

2.97 

3.34 

8 

0.42 

0.85 

1.27 

1.70 

2.12 

2.55 

2.97 

3.39 

3.82 

Q 

9 

0.480.96 

1.43 

1.91 

2.39 

2.87 

3.34 

3.82 

4.30 

10 

0  .53  1  .06 

1.59 

2.12 

2.65 

3.18 

3.71 

4.24 

4.78 

Depth    of    irriga- 

12 

0  .64  1  .27 

1.91 

2.55 

3.18 

3.82 

4.46 

5.09 

5.73 

tion  in  inches  if 

15 

0.801.59 

2.38 

3.18 

3.98   4.78 

5.58 

6.37 

7.17 

applied    for    24 

20 

1.06 

2.12 

3.18 

4.24 

.5  .30 

6.37 

7.43 

8.49 

9.56 

hrs.  every 

30 

1.59 

3.19 

4.78 

6.37 

7.96 

9.5511.14 

12.72 

14.32 

40 

•2.12 

4.25 

6.38 

8.49 

10.01  12.73  14  .85 

16.97 

19.10 

50 

2.65 

5.31 

7.96 

10.60 

13  .26  15  .92  18  .56 

21.21 

23.87 

60 

3.18 

6.37 

9.56 

12.72 

15.91 

19.10 

22.28 

25.47 

28.64 

1  00 

1.61 

3.23 

4.84 

6.46 

8.07 

9.69 

11.30 

12.91 

14.53 

.90 

1.45 

2  .90  4  .35 

5.81 

7.26 

8.72 

10.1711.61 

13.07 

.80 

1.29 

2  .58  3  .87 

5.16 

6.45    7.74 

9.04 

10.3211  .61 

.70 

1.13 

2  .26  3  .38 

4.52 

5.64    6.77 

7.90 

9  .04  10.17 

M 

.60 

.97 

.94  2  .90 

3.87 

4.84 

5.80 

6.77 

7.74 

8.72 

.50 

.81 

.6l!2.42 

3.23 

4.03 

4.84 

5.64 

6.45 

7.26 

Annual    depth    of 

.45 

.73 

.45  2  .18 

2.90 

3.63 

4.35 

5.08 

5.82    6.54 

water     in     feet 

.40 

.65 

.2911  .94 

2.58 

3.23 

3.87 

4.52 

5.16 

5.81 

for       irrigation 

.35 

.56 

.13  1  .69 

2.26 

2.82 

3.39 

3.95 

4.52 

5.09 

factors. 

.30 

.48 

.97 

1.45 

1.94 

2.42 

2.90 

3.38 

3.87 

4.35 

.25 

.40 

.81 

1.21 

1.61 

2.02 

2.42 

2.82 

3.23 

3.63 

.20 

.32 

.65 

.97 

1.29 

1.61 

1.94 

2.26 

2.58 

2.90 

.15 

.24 

.48 

.72 

.97 

1.21 

1.45 

1  .69 

1.94 

2.18 

.10 

.16 

.32 

.48 

.65 

.81 

.97 

1.13 

1.29 

1.45 

TABLE  III. 
ACRE-FEET  CONVERSION  TABLE. 


Acre-ft. 

Acre-in. 

Cu.  ft. 

Gals. 

Cu.  ft.  per  sec. 
for  a  day 

Gals,  per 
min.  for  a 
day 

1 

12 

43,560 

325,880 

.50416 

226.29 

2 

24 

87,120 

651,760 

1.0083 

452.6 

3 

36 

130,680 

977,640 

1  .5125 

678.9 

4 

48 

174,240 

1,303,520 

2  .0166 

905.2 

5 

60 

217,800 

1,629,400           2.5208 

1,131  .5 

6 

72 

261,360 

1,955,280 

3  0250 

1,357.7 

7 

84 

304,920 

2,281  ,160 

3.5292 

1,584.0 

8 

96 

348,480 

2,607,040 

4  .0332 

1,810.3 

9 

108 

392,040 

2,932,920 

4.5374 

2,036  .6 

18 


PRACTICAL  IRRIGATION. 


TABLE   IV. 
ACRE-INCH   CONVERSION  TABLE. 


Acre-in. 

Acre-ft. 

Cu.  ft. 

Gals. 

Cu.  ft. 
per  sec.  for 
a  day 

Gals, 
per  min.  for 
a  day 

1 

.08333 

3,630 

27,157 

.04201 

18  .858 

2 

.16667 

7,260 

54,314 

.08403 

37.72 

3 

.25000 

10,890 

81,470 

.12604 

56.58 

4 

.33333 

14,520 

108,627 

.16805 

75.43 

5 

.41667 

18,150 

135,784 

.21007 

94.29 

6 

.50000 

21,780 

162,940 

.25208 

113.15 

7 

.58333 

25,410 

190,099 

.29409 

132  .01 

8 

.66667 

29,040 

217,254 

.33611 

150  .86 

9 

.75000 

32,670 

244,410 

.37812 

169  .72 

10 

.83333 

36,300 

271,567 

.42013 

188  .58 

11 

.91667 

39,930 

298,724 

.46215 

207  .44 

12 

1  .00000 

43,560 

325,880 

.50416 

226  .29 

TABLE   V. 
CUBIC-FEET  CONVERSION   TABLE. 


Cu.  ft. 

Gals. 

Cu.  ft. 

Gals. 

per  sec.  for 

per  min.  for 

Acre-ft. 

Acre-in. 

a  day 

a  day 

10,000 

74,805 

.11574 

51  .948 

.22956 

2  .7548 

20,000 

149,610 

.23148 

103  .90 

.4591 

5.510 

30,000 

224,415 

.34722 

155  .85 

.6887 

8.265 

40,000 

299,220 

.46296 

207  .79 

.9182 

11  .019 

50,000 

374,025 

.57870 

259  .74 

1  .1478 

13  .774 

60,000 

448,830 

.69444 

311  .69 

1  .3774 

16  .529 

70,000 

523,635 

.81018 

363  .64 

1  .6070 

19  .284 

80,000 

598,440 

.92592 

415  .58 

1  .8365 

22  .038 

90,000 

673,245 

1  .4066 

467  .53 

2.066 

24  .793 

TABLE   VI. 
GALLONS  CONVERSION  TABLE. 


Cu.  ft. 

Gals. 

Gals. 

Cu.  ft. 

Acre-ft. 

Acre-in. 

per  sec.  for 

per  min.  for 

a  day 

a  day 

100,000 

13,368 

.30689 

3  .6827 

.15468 

69  .444 

200,000 

26,736 

.6138 

7.365 

.3094 

138  .89 

300,000 

40,104 

.9207 

11  .048 

.4640 

208  .33 

400,000 

53,472 

1  .2276 

14  .731 

.6187 

277  .78 

500,000 

66,840 

1  .5345 

18.414 

.7734 

347  .22 

600,000 

80,208 

1  .8413 

22.096 

.9279 

416  .66 

700,000 

93,576 

2.1482 

25  .779 

1  .0826 

486  .11 

800,000 

106,944 

2  .4551 

29  .462 

1  .2374 

555  .55 

900,000 

120,312 

2  .7620 

33  .144 

1  .3921 

624  .99 

UNITS    IN    USE.  19 

TABLE  VII. 
CUBIC  FEET  PER  SECOND  FOR  A  DAY,  CONVERSION  TABLE. 


Cu.  ft. 

Gals. 

per  sec. 

per  inin.  for 

Acre-  ft. 

Acre-in. 

Cu.  ft. 

Gals. 

for  a  day 

a  day 

1 

448.83 

1.9834 

23.80 

86,400 

646,315 

2 

897.7 

3.967 

47.60 

172,800 

1,292,630 

3 

1,346.5 

5.950 

71.40 

259,200 

1,938,945 

4 

1,795  .3 

7.934 

95.20 

345,600 

2,585,260 

5 

2,244  .2 

9.917 

119.00 

432,000 

3,231,575 

6 

2,693  .0 

11  .900 

142.80 

518,400 

3,877,890 

7 

3,141  .8 

13.884 

166.60 

604,800 

4,524,205 

8 

3,590  .6 

15  .867 

190.40 

691,200 

5,170,520 

9 

4,039  .5 

17.850 

214  .20 

777,600 

5,816,835 

TABLE   VIII. 
GALLONS  PER   MINUTE  FOR  A  DAY,  CONVERSION  TABLE. 


Gals. 

Cu.  ft. 

per  min. 

per  sec.  for 

Acre-ft. 

Acre-in. 

Cu.  ft. 

Gals. 

for  a  day 

a  day 

100 

.2228 

.4419 

5.303 

19,250 

144,000 

200 

.4456 

.8838 

10.606 

38,500 

288,000 

300 

.6684 

1  .3257 

15.909 

57,750 

432,000 

400 

.9812 

1  .7676 

21  .212 

77,000 

576,000 

500            1  .1140 

2  .2095 

26  .515 

96,250 

720,000 

600 

1  .3368 

2  .6514 

31  .818 

115,500 

864,000 

700 

1  .5596 

3  .0933 

37.121 

134,750 

1,008,000 

800 

1  .7824 

3  .5352 

42  .424 

154,000 

1,152,000 

900 

2.0052 

3  .9771 

47.727 

173,250 

1,296.000 

CHAPTER  III. 
METHODS  OF  IRRIGATION  IN  USE. 

BRIEFLY  stated,  the  following  are  the  methods  of  irrigation 
employed : 

1.  Flooding  (the  entire  surface  of  the  ground  being  wet), 
(a)  Land  is  divided  into  checks  by  contour  lines  from  3  inches 

to  10  inches  vertical  distance  apart,  and  a  small  levee  thrown 
up  all  around  each  check  into  which  the  water  is  admitted  till 
the  check  is  flooded. 

(6)  Bed  system,  where  the  land  is  divided  by  small  levees  into 
long  rectangles,  and  water  is  admitted  at  the  upper  end  at 
several  places,  passing  over  the  land  in  a  sheet. 

(c)  Contour  ditch  and  tablet  irrigation,  where  the  water  is 
admitted  from  cuts  in  the  ditch  bank  and  spread  over  the  land. 
This    requires    considerable    attention    to    make    a    uniform 
distribution. 

(d)  Wild    flooding.     Water  is    spread    over    large    areas    of 
land  from  a  few  outlets.     This  results  in  very  unequal  distri- 
bution. 

2.  Furrow   system,  where  the  water  is  admitted  to  furrows 
usually  from  12  inches  to  4  feet  apart  and  flows  through  them, 
sinking  into  the  ground  and  not  wetting  the  entire  surface. 

3.  Basin  system,  where  the  water  is  admitted  to  small  basins 
or  checks  around  trees.    This  system  is  used  mainly  for  young 
trees. 

4.  Sprinkling  by  revolving  water  witches  or  sprinklers,  which 
are  usually  allowed  to  run  in  one  place  for  from  1  to  2  hours. 

5.  Hand  sprinkling  from  a  hose. 

In  estimating  the  cost  of  applying  water,  there  are  two  bases 
on  which  it  can  be  figured: 

1.  Cost  of  applying  1  acre-foot. 

2.  Cost  of  irrigating  1  acre. 

Provided  the  quantity  of  water  it  is  desirable  to  apply  is  not 
exceeded,  the  first  method  gives  preferable  results  in  comparing 

20 


METHODS    OF   IRRIGATION   IN    USE.  21 

costs  of  application.  Hence  in  this  event  the  flow  which  one 
man  can  handle  determines  the  efficiency  of  application. 

Flooding  by  contour  checks  usually  allows  the  handling  of 
much  larger  streams  per  man  than  any  other  system  if  the 
ground  slope  is  suitable.  However,  it  usually  necessitates  the 
application  of  a  greater  depth  of  water  than  the  other  systems. 
A  small  flow  of  water  cannot  be  used  to  advantage,  since  it 
results  in  a  very  wasteful  and  inefficient  distribution. 

The  furrow  system  has  a  very  important  advantage  over 
flooding  or  sprinkling  systems  of  irrigation,  in  that  the  entire 
surface  of  the  ground  is  not  wet,  resulting  in  less  evaporation 
loss,  in  applying  the  water  nearer  the  roots  of  the  plants  and  in 
promoting  deep  rooting  of  plants,  the  roots  reaching  farther 
down  where  they  are  protected  from  the  surface  heat  and  can 
draw  on  the  moisture  deeper  in  the  soil.  If  the  soil  bakes  when 
wet,  the  furrow  system  should  be  used  instead  of  flooding,  and  the 
furrows  cultivated  as  soon  as  sufficiently  dry,  thus  preventing 
baking,  and  keeping  a  fine  protective  mulch  of  earth  over  the 
moist  earth,  preventing  rapid  loss  by  evaporation. 

However,  the  furrow  system  will  not  allow  handling  of  as 
great  quantities  of  water  per  man  as  flooding  by  contour  checks, 
and  will  generally  cost  more  for  labor  per  unit  quantity  of  water 
applied  and  per  irrigation. 

Sprinkling  systems  are  employed  mainly  in  the  East,  where 
the  irrigated  farms  are  very  small.  They  are  much  used  for 
truck. 

The  cost  of  sprinkling  by  revolving  water-witches  is  independ- 
ent of  the  depth,  and  is  dependent  only  on  the  cost  per  irriga- 
tion for  moving  the  apparatus. 

Hand  sprinkling  is  directly  dependent  on  the  quantity  of 
water  applied,  and  is  very  expensive.  The  stream  handled  by  a 
man  is  small.  Hence  irrigation  by  this  means  is  very  light,  in 
many  cases  not  exceeding  0.25  inch.  Such  irrigation  is  very 
inefficient  since  a  large  percentage  of  water  is  lost  by  evaporation. 
It  is  better  to  apply  one  1-inch,  than  four  0.25-inch  irrigations. 
Hand  sprinkling,  however,  has  the  advantage  of  allowing  a 
light  irrigation  to  be  quickly  given  to  a  large  area.  From 
investigations  by  the  author  in  Southern  Texas  and  in  the 
Eastern  States  the  following  information  has  been  compiled  as 
to  irrigation  practice  along  the  lines  laid  down.  This  informa- 


22  PRACTICAL  IRRIGATION. 

tion  was  obtained  from  a  large  number  of  plants,  many  of  which, 
as  might  be  expected,  were  radically  different. 

In  irrigation  by  checks,  the  sizes  of  checks  vary  from  0.25  to 
200  acres.  The  latter  is  many  times  too  large,  and  is  not  to  be 
recommended.  It  was  used  in  the  irrigation  of  rice.  For  other 
crops,  checks  usually  vary  from  0.25  to  10  acres,  the  proper  size 
depending  on  the  soil  slope  and  flow  of  water  available. 

In  bed  irrigation  the  length  of  bed  will  vary  between  100  and 
700  feet,  being  usually  from  100  to  250  feet  long. 

The  width  varies  from  10  to  50  feet,  usually  lying  between 
10  and  20  feet. 

The  flow  per  bed  varies  from  200  to  1000  gal.  per  min.,  requir- 
ing between  3  and  20  minutes  to  pass  over  the  bed. 

3.  Tablets  vary  from  300  to  1200  feet  in  length,  and  from  25 
to  65  feet  in  width. 

4.  Furrows  vary  in  length  from  40  to  600  feet,  and  are  run 
from  1  foot  to  4  feet  apart.     It  is  usually  good  practice  to  run 
furrows  from  100  to  300  feet  long.     If  too  long,  the  distribution 
of  water  is  very  uneven;  and  if  too  short,  the  labor  of  changing 
the  water  is  too  great.     If  the  ground  absorbs  water  rapidly, 
the  furrows  should  be  comparatively  short;  but  if  water  sinks 
in  slowly,  they  should  be  longer. 

The  time  to  run  through  the  furrows  varies  between  5  and  500 
minutes,  usually  varying  between  15  and  150  minutes.  Values 
of  flow  per  furrow  vary  from  5  to  300  gal.  per  min.  The  best 
practice  usually  lies  between  10  and  30  gal.  per  min.  Too  low 
a  value  of  flow  tends  to  effect  an  unequal  distribution,  and  too 
great  a  value  of  flow  will  tear  away  the  furrow.  In  orchard 
irrigation  the  water  sometimes  runs  continuously  in  the  fur- 
rows for  two  to  three  days.  This  information  gives  an  approx- 
imate idea  of  the  limits  of  irrigation  practice  for  various  methods 
of  irrigation. 


CHAPTER  IV. 
EVAPORATION. 

THE  efficiency  of  irrigation  water  may  be  measured  by  the 
actual  useful  work  performed  by  a  given  quantity  of  water.  To 
increase  the  efficiency,  requires  a  careful  investigation  of  the 
reasons  for  the  loss  of  water.  Evaporation  is  responsible  for 
many  of  the  greatest  losses  of  water,  both  from  reservoirs,  and 
from  the  land  itself.  Evaporation  consists  in  the  absorption  of 
water  in  the  form  of  vapor  by  the  air.  It  should  not  however 
be  confused  with  the  transpiration  losses  of  plants,  which  while 
they  may  be  included  under  the  same  general  heading,  have,  as 
has  been  pointed  out,  important  points  of  difference  in  the  laws 
they  follow. 

The  air  is  capable  of  containing  in  suspension  a  certain  amount 
of  moisture  in  the  form  of  an  invisible  vapor.  This  quantity  de- 
pends on  the  temperature,  and  increases  rapidly  with  increase  of 
temperature,  as  is  shown  in  the  following  table. 


WEIGHTS  OF  DRY  AIR,  AND  OF  THE  MOISTURE  OF  SATURA- 
TION,  PER  CUBIC   FOOT,  AT  PRESSURE   OF   29.92   INCHES 
OF  MERCURY. 


Temperature.      Degrees 

Fahr. 

Weight  of  1  cu.  ft.  of  dry  uir. 
pound 

Weight  of  vapor  in  1  cu.  ft. 
of  saturated  mixture, 
pound 

0 

0.0864 

0.000079 

32 

0.0807 

0.000304 

52 

0.0776 

0.000627 

62 

0.0761 

0.000881 

72 

0.0747 

0.001221 

82 

0.0733 

0.001667 

92 

0.0720 

0.002250 

102 

0.0707 

0.002997 

112 

0.0694 

0.003946 

122 

0.0682 

0.005142 

132 

0.0671 

0.006639 

23 


24  PRACTICAL  IRRIGATION. 

When  air  contains  its  maximum  amount  of  vapor,  it  is  said  to 
be  saturated,  and  any  diminution  of  temperature  will  result  in  a 
deposition  of  moisture  from  the  air.  From  the  table  it  appears 
that  one  cubic  foot  of  air  at  132°  F.  can  hold  84  times  as  much 
moisture  as  at  0°  F.  When  air  which  is  not  saturated  is  in  con- 
tact with  a  moist  surface,  it  will  tend  to  absorb  moisture  there- 
from. The  actual  rate  of  absorption  or  evaporation  will  depend 
not  only  on  the  percentage  of  saturation  of  the  air,  but  also  on 
the  temperature  of  both  the  air,  and  of  the  surface,  and  in  par- 
ticular on  their  temperature  just  where  they  are  in  contact. 
The  higher  the  temperature  of  either,  other  conditions  remaining 
constant,  the  more  rapid  the  evaporation.  The  important  rela- 
tion between  the  absorptive  power  of  the  air,  and  its  tempera- 
ture as  given  in  the  preceding  table,  is  worthy  of  particular  note, 
owing  to  the  high  evaporation  losses  in  irrigation.  Wind  will 
greatly  increase  the  evaporation  due  to  the  more  intimate  con- 
tact of  the  air  and  the  moist  surface,  be  it  a  water  surface,  or  the 
surface  of  the  ground.  Thus,  for  example,  different  experimenters 
state  that  wind  will  increase  the  evaporation  at  percentages  per 
mile  of  wind  per  day,  varying  between  0.5  per  cent  and  2  per 
cent.  It  is  doubtful  whether  any  such  simple  relation  may  be 
obtained  between  these  two  quantities,  particularly  in  view  of 
the  wide  divergence  of  the  results.  So  many  elements  enter  into 
the  problem  in  practice  that  without  ascertaining  the  effect  of 
each  one,  it  is  difficult  to  reach  satisfactory  conclusions.  The 
rapidity  of  evaporation  is  largely  dependent  on  the  dryness  of  the 
air.  The  condition  of  the  air  with  reference  to  moisture  is  usually 
expressed  as  the  per  cent  of  humidity,  i.e.,  the  per  cent  of  satura- 
tion moisture  the  air  contains.  Thus  it  is  evident  that  the  evap- 
oration is  dependent  on  the  six  following  conditions: 

1.  Area  of  the  surface  in  contact  with  the  air. 

2.  Temperature  of  the  surface. 

3.  Temperature  of  the  air. 

4.  Wind  velocity. 

5.  Per  cent  humidity  of  the  air. 

6.  Atmospheric  pressure. 

The  temperature  of  the  body  is  dependent  on  the  amount  of 
heat  which  it  will  receive,  the  amount  of  heat  which  it  will  trans- 
mit elsewhere,  and  on  its  ability  to  absorb  heat.  Excluding 
chemical  changes  and  electrical  manifestations,  there  are  three 


EVAPORATION.  25 

methods  of  the  usual  exchange,  or  transference  of  heat:  —  con- 
duction, convection,  and  radiation. 

Heat  of  conduction  is  heat  which  is  transmitted  through  a 
body  itself,  or  from  one  body  to  another.  Heat  of  convection  is 
heat  which  is  carried  away  by  transference  to  another  body  which 
is  then  transported;  as  for  example,  heat  carried  away  by  air 
currents.  Heat  of  radiation  is  heat  which  is  transmitted  through 
the  ether  as  radiant  energy;  such  as  the  heat  of  the  sun. 

If  equal  quantities  of  heat  be  applied  to  equal  weights  of  differ- 
ent bodies,  then  the  rise  in  temperature  will  depend  on  the 
nature  of  the  substance.  Water  has  many  times  the  heat  storage 
capacity  of  most  other  substances,  and  hence  will  not  rise  nearly 
as  much  in  temperature  as  other  materials,  under  the  similar 
conditions  just  outlined. 

The  radiant  energy  which  a  body  can  receive,  or  transmit, 
depends  on  the  color,  and  the  nature  of  the  surface.  Polished 
and  light  colored  surfaces  will  reflect  radiant  energy,  and  will  not 
absorb  as  much  heat  as  dark  surfaces.  It  is  well  known  that 
light  surfaces  will  not  become  as  warm  as  dark  surfaces  when 
exposed  to  the  sun.  Hence  the  surface  of  the  soil,  when  exposed 
to  the  sun,  will  become  far  hotter  than  a  wrater  surface  under 
similar  conditions,  and  if  the  soil  surface  be  saturated  with 
water,  the  loss  by  evaporation  will  be  far  greater  than  from  the 
water  surface.  The  reasons  for  this  are  fourfold : 

1.  The  water  will  reflect  a  large  amount  of  radiant  energy 
which  the  soil  will  absorb. 

2.  The  transmission  of  heat  by  conduction  is  greater  in  water 
than  in  the  soil.    The  earth  being  a  poor  conductor  of  heat,  the 
temperature  effects  due  to  the  daily  variation  are  confined  to 
the  surface  layers,  and  are  thus  intensified  at  the  surface. 

3.  The  specific  heat  of  water  being  greater  than  that  of  earth, 
the  temperature  rise  of  the  earth  will  be  greater  than  that  of  the 
water. 

4.  The  irregular  surface  of  the  ground  will  allow  a  greater  sur- 
face area  in  contact  with  the  air,  than  is  the  case  with  water. 

That  these  facts  are  true,  is  amply  borne  out  by  the  results  of 
experiments.  Thus  Professor  Fortier  in  some  experiments  on 
evaporation  found  that  under  the  conditions  of  the  tests,  the 
evaporation  from  a  saturated  soil  was  2.5  times  the  rate  of  evap- 
oration from  water  surfaces.  The  rate  of  evaporation  from  the 


26  PRACTICAL  IRRIGATION. 

soil  will  of  course  vary  greatly  with  the  moisture  in  the  top  layer, 
decreasing  rapidly  as  the  soil  becomes  dryer.  There  are  so  many 
different  elements  entering  into  the  rate  of  evaporation,  that  we 
must  be  careful  not  to  apply  experimental  or  other  data  to  cases 
to  which  they  do  not  belong.  The  results  of  both  experiment 
and  theory  show  that  the  rate  of  evaporation  is  directly  depend- 
ent on  the  amount  of  moisture  in  the  upper  layer  of  soil,  the  tem- 
perature, the  percentage  humidity  of  the  air,  and  the  wind 
velocity. 

It  will  be  natural  to  expect  a  greater  increase  of  temperature, 
and  hence  higher  evaporation  in  the  case  of  dark  soils  than  in  the 
case  of  light  soils,  due  to  the  greater  amounts  of  heat  absorbed. 
This  will  undoubtedly  be  true  provided  the  only  physical  differ- 
ence between  the  light  and  dark  soils  consists  in  the  color.  There 
are,  however,  other  elements  which  enter  into  the  problem. 
Thus  a  soil  which  tends  to  crack  open  will  facilitate  evaporation. 
Some  soils  possess  greater  capillary  power  than  others,  and  will 
tend  to  draw  water  to  the  surface.  The  top  layer  being  kept 
moist  will  of  necessity  cause  greater  evaporation.  This  is  notably 
true  of  alkali  soils. 

The  dryer  the  top  layer  of  soil,  the  less  will  be  the  evaporation 
loss.  The  moisture  from  below  the  surface,  before  evaporating, 
must  first  pass  through  the  top  layers,  to  which  it  is  drawn  by 
capillary  action.  Whatever  circulation  of  air  exists  in  the 
ground  will  also  have  some  effect  in  assisting  evaporation. 

Heat  will  have  the  effect  of  increasing  considerably  this  action. 
Hence  the  best  way  to  conserve  the  moisture  in  the  ground  is  to 
protect  it  both  from  heat,  and  from  contact  with  the  air,  and  not 
.  to  wet  the  surface.  Dry  sand,  or  earth  in  a  finely  subdivided 
state  is  an  excellent  nonconductor  of  heat,  owing  in  large  part  to 
the  great  multitude  of  air  spaces  between  the  particles.  The  air 
being  practically  confined  has  little  opportunity  to  circulate,  and 
to  transmit  heat  by  convection.  A  good  mulch  of  dry  earth  will 
be  very  effective  in  preventing  evaporation  losses.  Extensive 
experiments  which  have  been  made  along  these  lines,  have  shown 
the  great  value  of  cultivation,  not  only  for  irrigated  lands,  but 
also  to  conserve  the  supply  of  moisture  so  necessary  for  dry 
farming. 

The  ground  should  be  cultivated  as  soon  as  possible  after  irri- 
gation, and  in  irrigating  as  little  surface  as  possible  should  be 


EVAPORATIOX.  27 

wet.  This  suggests  that  sub-irrigation  by  buried  pipes  would  be 
the  most  efficient.  This  has  been  tried  in  a  few  instances,  but  as 
yet  has  proven  rather  impractical  owing  to  the  high  first  cost, 
and  to  the  difficulty  of  effecting  an  equal  distribution  of  water. 
The  roots  of  the  plants  which  are  naturally  lured  to  moisture,  in 
time  will  clog  up  the  openings  in  the  pipes,  and  the  pipes  them- 
selves. In  some  cases  if  the  subsoil  be  deep  and  gravelly,  much 
water  may  run  to  waste;  also  the  distribution  of  water  is  apt 
to  be  uneven  since  water  will  percolate  vertically  more  rapidly 
than  horizontally. 

From  the  standpoint  of  economy  the  deep  furrow,  i.e.,  from 
6  to  12  inches  deep,  will  in  many  cases  give  the  best  results. 
There  are,  however,  objections  to  deep  furrows  for  some  classes 
of  work,  owing  to  the  increased  cost  of  furrowing  and  culti- 
vation, and  because  deep  furrows  may  injure  shallow-rooted 
trees.  On  the  other  hand,  deep  furrowing  promotes  deep  root- 
ing of  trees,  which  will  thus  have  a  greater  supply  of  both 
moisture  and  fertilizer  from  which  to  draw. 

In  bulletin  No.  177  of  the  Office  of  Experiment  Stations, 
United  States  Department  of  Agriculture,  Professor  Fortier  gives 
the  results  of  many  interesting  experiments  to  determine  the  loss 
of  water  by  evaporation  from  the  soil,  which  show  in  particular 
the  importance  of  deep  cultivation  in  conserving  the  supply  of 
moisture  in  the  ground.  The  roots  of  trees  and  plants  will  natur- 
ally spread  where  they  can  obtain  moisture  from  the  soil.  In  a 
wet  season  when  the  ground  is  kept  moist  by  frequent  rains, 
shallow  rooting  is  encouraged,  and  when  the  upper  layers  of  the 
soil  become  dry  in  the  dry  season,  these  roots  are  of  no  value, 
and  will  wither.  Deep  cultivation  prevents  the  formation  of 
roots  in  the  surface  soil,  and  makes  them  go  further  downwards, 
where  they  will  be  of  use  during  dry  seasons.  Thorough  and 
deep  cultivation,  through  lessening  evaporation,  will  prevent 
both  the  rise  of  injurious  salts,  and  also  the  rise  of  those  salts 
which  are  beneficial  for  vegetation,  and  the  removal  of  the 
latter  from  the  zone  of  the  roots. 

The  following  figures  give  a  brief  summary  of  some  of  professor 
Fortier's  experiments.  The  experiments  on  the  evaporation 
from  soils  wrere  conducted  in  tanks  of  two  sizes,  23.5  inches  in 
diameter  and  47  inches  deep,  and  17  inches  in  diameter  and  30 
inches  deep  respectively,  which  were  filled  with  earth  and  set 


28 


PRACTICAL  IRRIGATION. 


flush  with  the  ground  so  as  to  imitate,  as  far  as  possible,  the  con- 
ditions of  the  rest  of  the  soil.  They  were  set  inside  other  tanks 
provided  with  a  water  jacket  to  facilitate  their  removal  for 
weighing. 

The  results  of  the  experiments  are  the  averages  of  a  number 
of  observations.  Most  of  the  experiments  were  conducted  in 
Southern  California  during  the  summer  and  fall. 

During  the  tests  at  Riverside  the  daily  average  temperatures 
reached  a  maximum  of  93°  F.  at  1  P.M.,  and  a  minimum  of  56°  at 
11  P.M.  and  5  A.M.  —  a  difference  of  37°.  The  average  difference 
between  the  12-hour  periods  of  day  and  night  was  24°.  At  the 
depth  in  the  ground  of  one  foot,  the  daily  temperature  variations 
practically  disappear.  All  temperatures  hereafter  will  be  given 
in  Fahrenheit.  While  the  temperatures  of  the  air  and  soil 
approach  each  other  during  the  early  morning  hours  before  the 
sun  gets  high,  the  soil  in  the  sun  at  1  P.M.  had  a  temperature  of 
117°,  while  the  air  in  the  sun  had  a  temperature  of  82°  at  the  same 
hour  —  a  difference  of  35°  in  the  case  of  these  experiments. 
From  another  series  of  experiments  of  nine  weeks  duration  the 
following  temperatures  were  obtained : 

AVERAGE  WEEKLY  TEMPERATURES  DURING  THE  DAY. 


Max. 

Min. 

Average 

Soil  in  the  sun   

117 

101 

106 

Air  in  the  sun    

90 

76 

84 

Dry  soil  in  the  shade  • 

88 

77 

83 

Water  in  tank    ....           

82 

78 

79 

Humid  soil  would  not  rise  as  high  as  dry  soil,  due  to  the  greater 
specific  heat,  and  to  the  greater  power  of  conduction,  as  well  as 
to  the  cooling  effect  due  to  evaporation.  Still  the  increase  of 
temperature  over  that  of  a  water  surface  is  ample  to  account  for 
the  effects  of  the  greatly  increased  evaporation,  as  is  shown  in  the 
following  table.  The  soil  was  a  sandy  loam,  and  the  tempera- 
tures were  a  mean  of  the  morning,  noon,  and  evening  tempera- 
tures. 


EVAPORATION. 


29 


EVAPORATION   FROM  MOIST  SOILS  AND  FROM  WATER 
SURFACES. 


Temperature,  Degrees  Fahr. 

Weekly  Evapora- 
tion 

Per  cent 

Air  in 

Soil  in 

Soil  in 

Moist 

Water 

Soil 

Water 

free   water 

shade 

shade 

sun 

soil 

surface 

inches 

inches 

Saturated 

71 

76 

95 

83 

77 

4.75 

1.88 

17.5 

76 

78 

106 

80 

1.33 

1.94 

11.9 

76 

78 

106 

80 

1.13 

1.94 

8.9 

76 

78 

108 

80 

.88 

1.94 

4.8 

76 

78 

108 

80 

.25 

1.94 

The  evaporation  from  water  surfaces  is  dependent  on  the  tem- 
perature, wind  and  humidity,  as  appears  from  the  following 
figures  for  two  stations,  Calexico  and  Chico.  Calexico  besides 
being  hotter  than  Chico,  is  also  much  dryer. 

EVAPORATION  FROM   WATER  SURFACES. 


Chico 

Calexico 

Min.  monthly  water  evaporation  in  inches  
Max  monthly  water  evaporation  in  inches  
Annual  water  evaporation  in  inches  

0.1 
10.0 
53 

2.7 
14.5 
89 

Max.  temperature  (monthlv)  

81 

93 

Min  temperature  (monthlv) 

45 

52 

The  following  results  were  obtained  by  heating  and  cooling 
water  in  tanks  in  the  field,  and  represent  the  average  of  four 
stations. 

EFFECT  OF  WATER  TEMPERATURE  ON  EVAPORATION  FROM 
WATER  SURFACES. 


Average  water  sur- 
face, temperature 

Average  daily  evap- 
oration, inches 

Average  water  sur- 
face, temperature 

Average  daily  evap- 
oration, inches 

53.4 
61.3 
73.5 

0.09 
0.19 
0.36 

80.4 
88.7 

0.48 
0.60 

With  average  wind  velocities  of  from  2.4  to  4  miles  per  hour, 
and  average  water  temperatures  of  70°,  the  increased  evaporation 
rate  due  to  wind  was  about  0.5  per  cent  per  mile  of  wind  per  day. 


30 


PRACTICAL  IRRIGATION. 


Experiments  on  soils  conducted  during  several  months  in  the 
dry  season,  where  about  two  inches  per  month  are  applied  to  the 
ground,  show  that  nearly  all  the  water  will  evaporate,  and  that 
poor  cultivation  is  of  little  value,  and  in  many  cases  is  positively 
detrimental.  In  a  very  sandy  soil,  where  the  water  will  drain 
through  readily,  poor  cultivation  is  of  some  advantage,  but  in  a 
soil  which  tends  to  retain  the  water  nearer  the  surface,  poor  cul- 
tivation may  cause  greater  evaporation  losses  than  no  cultiva- 
tion. 

Experiments  lasting  three  months,  which  were  conducted  to 
show  the  relation  between  the  quantity  of  water  applied  and  the 
evaporation  loss,  show  that  the  following  equation  holds  true. 

Evaporation  =  a  +  b  X  (the  depth  applied), 

where  a,  and  &,  are  constants. 

In  the  case  of  one  test  the  initial  free  moisture  was  7.7  per  cent 
and  was  equivalent  to  3  inches  of  water.  Irrigation  water  was 
applied  every  two  weeks,  and  the  constants,  a  and  &,  at  the  end  of 
three  months  were  a  =  1.3,  b  =  .66.  The  total  depth  applied 
varied  from  3.3  inches  to  9.8  inches. 

The  effect  of  cultivation  is  shown  in  the  following  tables. 
Water  was  applied  in  4-inch  furrows,  the  duration  of  application 
being  two  days. 

The  average  temperature  during  the  day  was  81°. 


EFFECT  OF  CULTIVATION  ON  EVAPORATION. 


Evapora- 
tion 
inches 

Water 
applied 
inches 

Initial  Moisture,  per  cent 

Loss  in  inches  in  first  5  days  un- 
cultivated      
Loss  in  inches  in  next  6  days  un- 
cultivated      

1.76 
1.39 

11.9 

Top  12  inches  dry 
6  per  cent  in  balance 

Loss  in  corresponding  period  (6 
days)  cultivated     

0.64 

of  soil 

Loss  in  inches  in  first  3  days  un- 
cultivated      

0.84 

8.0 

Loss  in  inches  in  next  3  days  un- 
cultivated   
Loss  in  corresponding  period  (3 
days)  cultivated     

0.29, 
0.10 

Top  4  inches  dry 

3  per  cent  in  balance 
of  soil 

EVAPORATION. 


31 


The  following  table  shows  the  effect  of  mulches  in  preventing 
evaporation,  and  is  most  instructive.  3.2  inches  of  water  were 
applied,  and  after  the  water  had  sunk  in,  mulches  of  various 
depths  were  added. 

Average  temperature  during  the  day  was  90°  F. 

EFFECT  OF  MULCHES  ON  EVAPORATION. 


Evaporation  in  inches 

First  3 
days 

Next  4 
days 

Next  4 
days 

Next  3 
days 

Total  for 
14  days 

No  mulch 

0.43 
0.13 
0.04 
0.01 

0.19 
0.03 
0.01 
0.00 

0.08 
0.03 
0.02 
0.01 

0.02 
0.02 
0.01 
0.00 

0.72 
0.21 
0.08 
0.02 

4-in.  mulch    
8-in   mulch 

10-in.  mulch  ... 

The  following  table  shows  the  effect  of  deep  furrows  in  con- 
serving the  moisture  in  the  ground.  The  ground  contained  4.5 
per  cent  of  free  moisture  at  the  start,  and  5.1  inches  of  water 
were  added  in  two  days,  and  on  the  third  day  the  ground  was 
cultivated. 

EFFECT  OF  DEPTH  OF  FURROW  ON  EVAPORATION. 

Average  Temperature  in  the  Shade,  82°  F. 


Losses  in  inches 


Days, 
land  2 

3 

4 

5  and  6 

7 

8  and  9 

10 

Total 

Surface  

0.73 

0.25 

0.10 

0.11 

0.01 

0.03 

0.00 

1.23 

3-in.  furrow  .    .    . 

0.63 

0.18 

0.13 

0.03 

0.02 

0.08 

0.02 

1.09 

6-in.  furrow  .    .    . 

0.52 

0.16 

0.10 

0.03 

0.01 

0.04 

0.02 

0.88 

9-in.  furrow  .    .    . 

0.44 

0.13 

0.10 

0.02 

0.05 

0.07 

0.00 

0.81 

12-in.  furrow  .    .    . 

0.34 

0.10 

0.10 

0.04 

0.03 

0.02 

0.00 

0.63 

In  another  case  where  2.1  inches  of  water  wore  applied  the  loss 
in  34  days  was  1.81  inches  when  using  3-inch  furrows,  and  .49 
inch  when  using  12-inch  furrows.  In  these  experiments  the 
ground  was  cultivated  as  soon  as  it  was  dry. 

To  show  the  effect  of  sub-irrigation,  water  was  applied  to  tanks 
at  various  depths.  The  free  moisture  in  the  ground  at  the  start 
was  equivalent  to  a  depth  of  4.4  inches,  and  a  2-inch  mulch  was 


32 


PRACTICAL  IRRIGATION. 


placed  on  top.  5.3  inches  of  water  were  applied.  The  evapo- 
ration losses  in  ten  days  were  as  follows,  the  average  temper- 
ature during  the  day  being  89°  F.  in  the  shade. 

EVAPORATION   FROM   SUB-IRRIGATED   SOILS. 


Depth  of  application 
in  inches 

Loss  in  inches 

3 

1.34 

6 

0.96 

9 

0.55 

12 

0.32 

Contrary  to  what  might  be  expected,  at  the  end  of  the  ten  days 
the  moisture  content  near  the  surface  was  greater,  the  deeper  the 
irrigation. 

The  following  table  shows  the  comparative  evaporation  losses 
for  sub-irrigation  at  two  feet  depth,  and  for  surface  irrigation. 
7.0  inches  of  water  were  added  in  four  applications,  a  week  apart. 

SUB-IRRIGATION  AND  SURFACE-IRRIGATION  EVAPORATION. 


Kind  of  soil 

Sub-irrigated 

Surface 
irrigated 

Sandy  loam                                                  .... 

0  74 

4  22 

Sandy  soil                                             

0  62 

3  64 

Dark  loam      

1  96 

5  63 

Average 

1  11 

4  49 

Alkali  soil  .    

2.81 

4.35 

Loss  in  inches  in  26  days 


Thus  in  the  case  of  sub-irrigation,  only  one-fourth  of  the  water 
lost  in  surface  evaporation  was  lost.  The  alkali  soil  was  not  in- 
cluded in  the  average,  since  alkali  tends  to  keep  the  surface  moist. 

From  the  standpoint  of  economy  of  water,  the  best  time  to 
irrigate  is  at  night,  or  in  the  evening.  In  many  cases  there  are 
objections  to  night  irrigation,  since  it  is  far  more  difficult  to  see 
properly  than  in  the  day  time,  and  also  since  in  the  majority  of 
cases,  water  must  be  used  continuously  where  there  is  no  reser- 
voir for  storing  it. 


EVAPORATION. 


33 


The  results  of  these  experiments  furnish  important  data  on  the 
quantitative  values  of  evaporation  losses,  and  show  to  what 
extent  they  may  be  avoided.  They  bring  out  with  particular 
force  the  actual  value  of  deep  furrows,  and  of  thorough  cultiva- 
tion. In  practice  the  evaporation  losses  will  be  less  than  in  the 
experiments,  due  to  the  effect  of  the  crop  in  shading  the  soil.  On 
the  other  hand,  there  will  be  a  loss  of  water  by  seepage  through 
the  subsoil,  which  loss  does  not  appear  in  the  case  of  tests  in  tanks. 
It  is  a  difficult  matter  to  ascertain  the  actual  evaporation  losses 
in  practice,  and  to  segregate  the  transpiration  and  evaporation 
losses  proper.  The  total  losses  from  transpiration  and  evapora- 
tion may  be  easily  arrived  at  by  growing  crops  in  the  tanks.  For 
further  description  of  the  work  the  reader  is  referred  to  Professor 
Fortier's  bulletin. 

In  the  Engineering  News  of  Sept.  19,  1907,  Professor  Fortier 
gives  the  results  of  experiments  made  under  his  direction  by 
Mr.  Frank  Adams  to  determine  the  influence  of  altitude  on 
evaporation.  The  experiments  were  made  on  the  Eastern  slope 
of  Mt.  Whitney,  California,  in  evaporation  tanks.  They  show  a 
steady  decrease  in  evaporation,  with  increasing  elevation.  All 
the  points  when  plotted,  lie  on  a  regular  curve,  with  the  excep- 
tion of  the  results  at  the  summit,  where  the  much  greater  expo- 
sure resulted  in  higher  losses.  The  fact  that  the  losses  decreased 
with  increase  of  altitude  is,  without  doubt,  due  to  the  lower 
temperatures,  at  higher  elevations,  which  more  than  compen- 
sated for  the  increased  evaporation  which  would  result  from 
lower  atmospheric  pressures.  The  following  table  gives  a  sum- 
mary of  the  tests. 

EVAPORATION   FROM   WATER   SURFACES,  ON  MT.  WHITNEY. 


Station 

Elevation 

Weekly  Evap- 
oration 

Soldiers  Camp       

Feet 
4,515 

Inches 
2  68 

Junction  South  Fork  and  Lone  Pine  Creeks   . 
Hunters  Camp 

7,125 
8  370 

2.04 
1  75 

Lone  Pine  Lake                                       

10,000 

1  63 

Mexican  Camp  .    .        

12,000 

1  60 

Summit  Mt  Whitney 

14  502 

1  67 

CHAPTER  V. 


ACTUAL  RESULTS   OF   IRRIGATION. 

ACCORDING  to  Professor  King,*  the  following  are  the  average 
irrigation  requirements  of  land  in  various  parts  of  the  world. 
The  results  were  given  in  acres  irrigated  per  cubic  foot  per  second, 
but  have  been  calculated  also  in  gallons  per  minute  per  acre. 

TABLE  IX. 
IRRIGATION  PRACTICE  IN  VARIOUS  PARTS  OF  THE  WORLD. 


Location 

Acres  per  cu.  ft. 
per  sec. 

Gal.  per  min. 

Av.  gal. 
per  min. 

North  India      

60  —  150 
65—    70 
80  —  120 
60  —  120 
80  —  100 
70—    90 
60—    80 
60—    80 
100  —  150 
100  —  150 
150  —  300 

7  .5  to  3  .0 
7  .0  to  6  .5 
5  .6  to  3  .7 
7  .5  to  3  .7 
5  .6  to  4  .5 
6  .4  to  5  .0 
7  .5  to  5  .6 
7  .5  to  5  .6 
5  .6  to  3  .0 
5  .6  to  3  .0 
3  .0  to  1  .5 

5.2 
6.2 
4.6 
5.6 
5.0 
5.7 
6.6 
6.6 
4.3 
4.3 
2.3 

Italy      

Colorado    

Utah      

Montana    

Wyoming      

Idaho                 

New  Mexico      .    . 

Southern  Arizona    

San  Joaquin  Valley     

Southern  California     

Rice  Irrigation     .... 

25—    66 

18.0  to  6.1 

12.0 

Professor  King  states  that  the  amount  of  water  required  per 
irrigation  to  wet  the  land  to  a  depth  of  4  to  5  feet  is  from  2.5 
inches  to  4.5  inches  for  land  fairly  moist,  and  from  3.75  inches 
to  11  inches  for  land  very  dry.  From  2  to  7  irrigations  are 
required  for  wheat  crops,  the  average  usually  being  between  3 
and  5.  From  experiments  on  earth  tanks  the  following  quanti- 
ties of  water  must  be  applied  to  produce  crops  of  one  ton,  the 
water  so  applied  making  up  the  evaporation  and  the  transpira- 
tion losses  of  the  crops: 

*  "Irrigation  and  Drainage,"  by  F.  H.  King. 
34 


ACTUAL    RESULTS    OF   IRRIGATION.  35 

Crop.  Acre-in.  per  ton 

Clover 5.1 

Oats 4  .4 

Karlry 4.1 

Maize 2.4 

The  weight  of  one  acre-inch  of  water  is  113  tons. 

As  these  tests  were  conducted  in  inclosures,  sheltered  from 
wind,  this  may  be  regarded  as  the  minimum  quantity  of  water  to 
grow  the  crops  without  allowing  for  either  probable  surface  loss 
or  under-drainage,  and,  in  general,  considerably  greater  amounts 
must  be  applied  to  raise  a  crop.  According  to  Professor  King's 
figures  it  takes  from  about  300  to  500  pounds  of  water  to  raise 
1  pound  of  dry  material  and  provide  for  the  transpiration  and 
evaporation  losses. 

According  to  Newell,  the  average  irrigation  requirements  are 
from  4  inches  to  6  inches  per  month.  This  corresponds  to  a 
flow  of  from  2.5  to  3.8  gal.  per  min.  per  acre.  In  Southern 
California  1  cu.  ft.  per  sec.  will  irrigate  from  250  to  500  acres, 
a  required  flow  of  1.8  to  0.9  gal.  per  min.  per  acre. 

Great  variations  will  be  found  in  the  depth  of  water  applied 
per  irrigation  in  different  places.  Very  shallow  irrigations  are 
generally  undesirable,  on  account  of  the  cost  of  application  and 
the  inefficiency  of  the  same,  due  to  the  high  percentage  of  evap- 
oration losses.  On  the  other  hand,  too  heavy  irrigation  results 
either  in  loss  due  to  seepage  of  the  water  through  the  ground, 
or  else  in  rendering  the  ground  too  wet,  and  hence  unfit  for  the 
growth  of  plants.  The  suitable  depth  of  irrigation  will  lie 
between  these  two  extremes,  and  will  depend,  among  other 
things,  on  the  depth  of  soil,  the  pore  space,  and  on  the  amount  of 
moisture  existing  in  the  soil  previous  to  irrigation. 

The  frequency  of  irrigation  should  be  governed  by  the  fact 
that  moisture  in  the  belt  of  soil  which  the  roots  penetrate,  should 
not  fall  to  a  point  where  the  crop  would  begin  to  show  signs  of 
failure,  but  should  be  kept  in  quantity  sufficient  for  plant  growth. 
Many  plants,  when  the  crop  is  maturing,  require  more  moisture 
than  at  other  stages  in  their  growth. 

While  it  is  impossible  to  lay  down  hard  and  fast  rules  for  irri- 
gation practice,  owing  to  the  diverse  conditions  encountered, 
the  figures  which  follow  give  a  summary  of  investigations  con- 
ducted by  the  author  and  show  the  irrigation  practice  in 


36 


PRACTICAL  IRRIGATION. 


various  parts  of  the  country.  It  is  to  be  noted  that  the  quantity 
"  required  flow  "  is  not  the  actual  rate  of  flow  provided  for, 
which  is  much  greater,  but  is  the  rate  which  would  be  required 
were  the  required  full  water  supply  to  run  continuously  during 
an  irrigation  season  without  rain.  In  many  places  the  plants 
are  far  too  large  for  the  land  they  must  irrigate,  and  in  other 
cases  the  plants  operate  only  during  the  daytime.  Hence  the 
required  flow  is  much  less  than  that  actually  provided  in  many 
places.  In  the  figures  to  follow,  two  methods  of  obtaining 
averages  are  used:  (1)  Straight  average,  found  by  dividing  the 
sum  of  the  averages  for  the  several  farms  by  the  number  of 
farms;  and  (2)  the  weighted  average,  found  by  dividing  the 
total  results  of  all  farms  by  the  total  size  of  the  farms.  These 
averages  will  be  materially  different,  and  the  former  will  represent 
the  average  result  of  the  individual  farmer,  while  the  latter 
represents  the  average  result  for  the  whole  country. 

Irrigation  water  is  usually  applied  in  depths  varying  from 
0.25  inch  to  8  inches  per  irrigation.  The  former  is  usually 
inefficient,  due  to  large  percentage  evaporation;  and  the  latter, 
unless  the  ground  has  a  deep  subsoil,  is  apt  to  prove  injurious 
from  over-saturation. 

TABLE  X. 
IRRIGATION   PRACTICE  IN  SOUTHERN  TEXAS. 


Crop 

Frequency 
of 
irrigation, 
days 

Irrigations 
per 
season 

Depth  of 
water  per 
irrigation, 
inches 

Depth  of 
water  per 
season, 
feet 

Required 
flow, 
Gal. 
per  min. 
per  acre 

Irrigation- 
factor, 
Per  cent 

Alfalfa     .... 
Cane    . 

38 
13 

9 

5 

5.1 
3  6 

5.72 
2  50 

2.5 
5  2 

93 
18 

Corn    . 

16 

3 

4  4 

1  53 

5  2 

13 

Cotton    .    .    . 
Johnson  grass 
Onions    .    .    . 
Rice        .    .    . 
Sorghum     .    . 
Truck  

21 
37 
11 

13 
12 

3 

7 
11 

'4' 
6 

5.5 
6.1 
2.4 

3^5 

2.8 

1.60 
3.51 
2.40 
5.12 
1  .86 
1  .30 

5.0 
3.1 
4.1 

5.6 
4.4 

17 
71 
33 
25 
14 
20 

Average      .    .    . 

4.2 

2.67 

In  general,  it  appears  that  efficient  depths  of  irrigation  per 
irrigation  vary  from  1  inch  to  6  inches;  the  best  depth  depending 


ACTUAL    RESULTS    OF   IRRIGATION. 


37 


on  the  soil,  crop,  climate,  and  cost  of  water,  as  well  as  the  cost 
of  applying  it. 

In  dry  weather,  truck  is  usually  irrigated  to  a  depth  of  from 
1  to  2  inches,  applied  every  7  to  14  days. 

Table  X  is  taken  in  part  from  investigations  by  the  writer  in 
Texas,  and  allows  for  ditch  losses.  It  is  based  on  straight 
averages. 

Owing  to  the  widely  varying  conditions  and  practice  of  the 
different  farms  making  up  these  tables,  and  to  the  method  of 
obtaining  averages,  these  results  will  not  check  exactly,  and  close 
results  must  not  be  expected.  However,  it  may  in  general  be 
stated  as  results  that  the  average  required  flow  per  acre  for  grass 
or  alfalfa  is  2.8  gal.  per  min.,  and  for  rice  is  12.3  gal.  per  min., 
while  for  other  crops  it  is  4.9  gal.  per  min.  These  figures  allow 
for  loss  in  seepage  in  the  distributing  ditches.  The  actual 
required  flow  will  vary  with  the  nature  of  soil,  climate,  crop,  and 
ditch  loss.  Considerable  latitude  in  either  direction  must  be 
allowed  in  applying  these  results  to  the  various  conditions  in 

practice. 

TABLE  XI. 

AVERAGE  RETURNS  FROM  IRRIGATED  CROPS  IN 
SOUTHERN  TEXAS. 


Crops 

Unit 

Crop  Yields 

Assumed 
value 
per  unit 

Value  of 
crop 
per  acre 

Alfalfa          

Ton 

5.9 

$15.00 

$88.50 

Corn      
Cotton       
Johnson  grass      
Onions      

Bushel 
Bale 
Ton 
Pound 

41  .0 
.8 
3.0 
18612.0 

.50 
50.00 
12.00 
.02 

20.50 
40.00 
36.00 
372.24 

Rice 

Pound 

2140  0 

.02 

42.80 

Sorghum       

Ton 

4.0 

TABLE   XII. 

AVERAGE   COSTS   OF  APPLYING  IRRIGATION  WATER 
IN  SOUTHERN  TEXAS. 

Cost  of  labor  per  day $0  .59 

Labor  per  irrigation  per  acre,  in  days .42 

Cost  per  irrigation  per  acre      $0  .31 

Labor  of  irrigation  per  acre  for  a  year,  in  days 3  .07 

Cost  of  irrigation  per  acre  for  a  year $1  .96 

To  the  cost  of  applying  water  must  be  added  the  cost  of  supply- 
ing water. 


38  PRACTICAL  IRRIGATION. 

The  results  from  pumping  plants  are  shown  in  Table  XIII, 
giving  total  costs  of  pumping  water  per  acre,  using  weighted 
averages. 

TABLE   XIII. 

TOTAL   COST  PER  ACRE   OF  PUMPING  WATER 
IN  SOUTHERN  TEXAS. 

Fuel  —  wood  — 

Rice  irrigation      $3 .34 

Other  crops 12  .04 


Average .    .    .    .         4 .73 

Coal-burning  Plants 11  .38 


Average  for  Steam  Plants       5  .91 

Gasoline  Plants 17 .46 

Summary  — 

Rice  irrigation       4 .87 

Other  crops 12.21 


Total  average 6  .13 

Rice  irrigation  plants  usually  operate  under  low  lift,  and  are 
of  large  size. 

These  costs  are  greater  than  is  usually  expected,  since  the 
fixed  expenses  form  from  one-half  to  two-thirds  of  their  total 
value. 

The  results  from  the  small  truck  farms  in  the  humid  East 
show  that  on  an  average  the  value  of  irrigation  is  over  $200  an 
acre  a  year  over  the  total  cost  thereof.  The  conditions 
encountered  in  humid  countries  are  quite  different  from  those 
in  arid  countries.  Usually  the  only  crops  irrigated  to  any 
extent  are  truck,  where  the  values  of  the  crop  are  exceedingly 
high.  Irrigation  is  of  very  great  value,  however,  but  owing 
to  the  small  sizes  of  the  farms  and  the  methods  of  irrigation 
used,  the  cost  is  exceedingly  high  per  unit  quantity  of  water. 
The  water  is  often  distributed  by  piping  at  very  high  first  costs 
and  high  cost  of  application.  With  pumping  plants  the  loss 
in  this  piping  involves  pumping  against  a  much  higher  head 
than  would  be  necessary  otherwise.  Often  city  water  is  used. 
Tables  XIV,  XV,  and  XVI  give  average  data  on  irrigation  in  the 
humid  East,  taken  from  several  farms,  where  the  conditions 
differed  greatly. 


ACTUAL  RESULTS    OF   IRRIGATION. 


39 


TABLE   XIV. 
COST    PER   ACRE    OF   IRRIGATION   IN   THE   EAST. 


System 

First  cost 

Annual  rust 
of  fuel  and 
operation  or 
of  water 

Fixed 
charges 

Total 

Annual 
depth 
inches 

City  water  .... 

$44 

916 

$9 

$25 

4 

Pump  plants   .    .    . 

74 

9 

1.5 

24 

8 

COST  OF   WATER  PER  ACRE-FOOT. 

City  water  $48. 

Pump  water  (fuel  and  labor  charges  only)  $13. 


TABLE  XV. 

COST  OF  APPLICATION   OF   WATER  BASED   ON  LABOR 
AT  $1.50   PER   DAY  IN   THE   EAST. 


System 

Gal.  per  min. 
per  unit 
stream 

Cost  per 
acre-foot 

Cost  per  acre 
per 
irrigation 

Depth  per 
irrigation,— 
inches 

Furrow     

24 

$7.10 

$0.75 

1  .3 

Hose     

44 

34.80 

1  .80 

.6 

Single  sprinkler  
Multiple  sprinkler  .... 

4 
4 

34.40 
16.10 

1  .12 

2.40 

.3 

1.8 

The  cost  of  application  per  acre-foot  is  proportional  to  the 
size  stream  handled  per  man.  Single  and  multiple  sprinklers 
require  only  a  part  of  the  time  of  one  or  more  men,  while  hose 
requires  their  entire  time,  costing  far  higher  per  unit  quantity 
of  water  applied. 

As  indicating  the  possible  field  for  irrigation  of  other  crops  in 
humid  climates,  Table  XVI  gives  the  average  difference  between 
crops  in  a  good  year,  which  irrigation  would  insure,  and  average 
crops  in  the  East. 

The  results  of  investigations  in  the  East  show  for  truck  a 
required  flow  per  acre  of  3.3  gal.  per  min.  and  give  the  following 
averages:  Frequency,  6  days.  Irrigations  per  crop  per  season, 
5.  Depth  per  crop,  5.6  inches.  The  frequency  given  would  be 
required  without  rainfall.  The  required  flow  is  to  be  contrasted 


40 


PRACTICAL  IRRIGATION. 


with  4.9  gal.  per  min.  in  Texas.  The  actual  average  flow  provided 
in  the  East  is  6.1  gal.  per  min.  per  acre,  and  as  the  plants  are  not 
usually  operated  at  night,  they  are  near  the  limit  of  irrigation. 

TABLE  XVI. 

AVERAGE  DIFFERENCE  BETWEEN  CROPS  IN  GOOD  AND 
AVERAGE  YEAR  PER  ACRE  IN  THE  EAST. 


Crop 

Unit 

Av.  yield 
per  acre 

Yield  in 
wet  year 

Assumed 
price 

Increased 
.     value  in 
good  year 

Corn      

bushel 

48 

64 

$0.60 

$14  .40 

Wheat  
Rve 

« 
u 

20 
20 

28 
25 

.83 

6.64 

Oats     

(t 

40 

52 

.37 

4.44 

Tobacco  .... 
Timothy  .... 
Clover      .... 

pounds 

tons 

ti 

1330 
1  .6 
1  .6 

1700 
2.1 
2.1 

.08 
13.00 
11  .00 

29.60 
6.50 
5.50 

In  the  East  most  of  the  distribution  was  by  piping,  resulting 
in  no  loss  of  water  in  the  ditches ;  also  the  climate  was  not  so 
warm  as  in  Texas.  Taking  these  facts  into  consideration,  the 
results  show  a  fairly  close  agreement.  As  has  been  shown, 
efficient  irrigation  consists  in  obtaining  the  maximum  benefit 
from  a  given  expenditure;  and  in  the  selection  of  the  system  of 
irrigation,  the  various  component  parts  of  the  cost,  and  the 
actual  effect  of  the  same,  should  be  considered  as  a  whole  as 
well  as  separately,  before  coming  to  a  decision. 

The  relative  costs  of  labor,  fuel,  and  machinery  have  an  impor- 
tant bearing  on  the  system  to  be  selected.  No  one  element  of 
cost  should  predominate  to  the  detriment  of  the  others.  The 
length  of  irrigation  season  has  a  most  important  effect  on 
the  proper  design.  For  a  short  season,  with,  say,  an  irrigation 
factor  of  from  10  to  20  per  cent,  generally  the  fixed  charges 
will  be  greater  than  labor  and  operating  charges.  Where 
labor  is  high,  it  will  not  pay  in  general  to  adopt  a  system  requir- 
ing excessive  labor  in  the  application  of  water  to  the  land. 

The  low  irrigation  factors,  which  are  quite  common,  suggest 
strongly  in  many  cases  the  advisability  of  minimizing  the  first 
cost.  In  many  instances  this  may  be  effected  by  the  use  of  a 
reservoir  or  earth  tank  of  small  capacity,  say  sufficient  to  hold 


ACTUAL    ItlM-LTS    OF   IRRIGATION.  41 

12  to  24  hours '  supply.  The  advantages  of  reservoirs  for  this 
purpose  will  be  treated  more  fully  farther  on. 

Where  labor  is  high  it  is  very  undesirable  to  incur  a  large 
expense  for  application  of  water.  The  irrigator  should  have, 
if  possible,  as  large  a  stream  as  he  can  handle  to  advantage, 
and  not  waste  his  time  distributing  small  quantities  of  water. 
It  is  usually  very  wasteful  to  attempt  to  distribute  from  a  pump, 
a  small  stream  of  water  direct  to  the  land.  Not  only  is  the 
seepage  loss  very  high, but  also  the  expense  for  labor  for  applying 
the  water  is  far  higher  than  should  be  the  case  were  a  reservoir 
to  be  used.  Note  particularly  the  cost  of  application  of  water  in 
the  East.  Only  the  exceedingly  high  profits  of  irrigation  allow 
such  extravagant  methods,  where  the  cost  of  irrigation  is  often 
higher  than  the  total  value  of  irrigated  crops  in  the  West. 

Truck  irrigation  in  the  East  frequently  saves  an  entire  crop 
and  may  be  worth  as  high  as  $1500  an  acre  a  year.  It  often 
enables  an  additional  crop  to  be  grown  in  a  season. 

From  a  number  of  plants  in  the  East  the  average  net  return 
per  acre  per  year  from  irrigated  farms  was  $1030,  $330  of  which 
was  due  to  irrigation,  the  total  cost  per  acre  of  which  lay  between 
$30  and  $100  per  season. 


CHAPTER  VI. 
DIFFERENT  SOURCES  OF  WATER  SUPPLY. 

THE  primary  consideration  in  an  irrigation  plant  is  the  source 
of  water  supply :  First,  with  reference  to  obtaining  the  right  to  use 
it;  second,  whether  the  supply  is  sufficient  for  the  needs  of  the 
land,  when  water  is  required;  and  third,  the  method  and  cost  of 
development.  The  prior  rights  of  other  parties  and  the  available 
supply  of  water  should  be  carefully  considered  before  going  to 
the  expense  of  actual  construction.  If  the  water  be  purchased 
from  a  water  company,  the  nature  of  the  contract  should  be 
carefully  examined,  to  determine  whether  the  applicant  is 
likely  to  receive  the  necessary  water  supply,  and  the  probability 
of  the  possible  failure  of  the  same.  Before  diverting  water 
from  a  stream  the  proper  state  officials  should  be  seen.  The 
state  engineer,  or  board  of  irrigation,  usually  has  control  of  such 
matters  in  the  West. 

The  Natural  Flow  of  Streams. 

The  most  common  and  most  important  source  of  irrigation 
water-supply  consists  in  utilizing  the  natural  flow  of  streams,  by 
diverting  water  therefrom.  Where  the  diversion  of  water  can  be 
made  cheaply  by  the  use  of  short  canals,  this  is  generally  the 
cheapest  and  best  source  of  supply,  provided  there  is  sufficient 
water  in  the  streams  when  required  for  irrigation.  The  flow  of 
the  rivers  and  streams,  however,  occurs  at  such  periods  that 
without  storage  much  of  the  water  will  go  to  waste,  and  can- 
not be  used  on  the  land.  Where  the  development  has  exceeded 
the  water  supply,  the  water  in  the  streams  will  often  fail  to 
furnish  an  adequate  supply  when  most  needed  for  irrigation. 
In  these  cases  the  land  must  get  along  as  best  it  can  without 
water. 

Where  the  rights  are  determined  by  priority,  the  last  comer  is 
the  first  to  suffer.  Where  the  rights  are  vested  in  a  canal  com- 


•e* 

42 


DIFFERENT   SOURCES    OF    WATER   SUPPLY.          43 

pany,  the  water  is  usually  pro-rated  to  the  various  users.  The 
flow  of  the  streams  and  the  probable  variation  of  the  same  with 
the  period  of  year,  as  well  as  the  difference  between  different 
years,  should  be  given  careful  consideration,  with  reference  to  the 
period  of  the  irrigation  season.  Where  the  watershed  is  rugged 
and  steep,  the  run-off  of  the  rain  water  is  usually  very  rapid. 
On  the  other  hand,  where  the  reverse  conditions  are  found,  the 
run-off  will  be  much  slower,  much  of  the  water  finding  its  way 
gradually  through  the  soil  into  the  river  bed,  appearing  in  the 
form  of  springs,  which  tend  to  equalize  the  flow. 

The  melting  snows,  from  which  many  of  the  rivers  are  fed, 
serve  as  a  valuable  source  of  water  storage,  preventing  the  rapid 
run-off  which  would  otherwise  occur.  Of  necessity  a  very  large 
part  of  the  supply  of  rivers  used  for  irrigation  will  run  to  waste, 
unless  the  water  be  stored.  This  has  led  to  the  construction 
of  many  large  reservoirs,  and  the  important  government  work 
undertaken  by  the  Reclamation  Service  will  vastly  increase  the 
available  irrigable  area. 

It  is  the  intention  of  the  government  to  deliver  these  dams  and 
irrigating  systems  to  the  settlers,  who  are  to  pay  for  the  work 
within  ten  years,  after  which  they  will  be  owned  and  controlled 
by  themselves  as  a  company.  The  construction  of  large  reser- 
voirs involving  great  sums  of  money  usually  calls  for  too  heavy 
an  expenditure  to  be  undertaken  by  private  individuals.  Per- 
haps the  most  useful  feature  of  the  use  of  reservoirs  in  irrigation 
work  is  the  fact  that  they  render  available  water  which  could 
not  otherwise  be  obtained;  and  indeed  they  are  not  governed  by 
the  previous  cost  of  water,  but  rather  ultimately  by  the  actual 
value  of  the  water.  This  will  be  discussed  more  fully  farther  on. 

Reservoirs. 

Reservoirs  may  be  divided  into  two  classes,  natural  and 
artificial.  In  the  first  class  are  included  reservoirs  where  the 
greater  part  of  the  retaining  banks  are  formed  by  nature;  while, 
on  the  other  hand,  artificial  reservoirs  are  those  in  which  prac- 
tically all  the  banks  are  constructed  artificially. 


44  PRACTICAL  IRRIGATION. 

Natural  Reservoirs. 

Natural  Reservoirs  are  used  for  the  storage  of  river  or  rain 
water,  not  only  for  its  various  economic  uses,  but  also  in  some 
cases  to  equalize  the  flow  of  rivers  and  to  minimize  the  danger 
of  floods. 

Preliminary  considerations: 

1.  Before  undertaking  the  construction  of  a  reservoir  a 
careful  consideration  should  be  given  to  the  source  and  extent 
of  water  supply,  drainage  area,  rainfall  and  distribution,  the 
nature  of  the  ground  with  reference  to  seepage  and  the  annual 
and  monthly  evaporation.  Among  other  considerations  the 
nature  of  the  soil  with  reference  to  salt  and  alkali  should  be 
taken  into  account,  in  order  that  the  stored  water  may  not  be 
contaminated  by  dissolving  the  salts  in  the  soil.  A  considera- 
tion of  the  losses  by  evaporation  shows  the  importance  of 
considerable  average  depth  of  water  in  the  reservoir,  as  well  as 
the  poor  policy  of  shallow  construction.  Efficiency,  which  is 
the  ratio  of  the  amount  of  water  taken  out  to  that  which  is  put 
into  the  reservoir,  should  be  determined  beforehand  as  closely  as 
possible.  The  efficiencies  of  reservoirs  vary  widely,  depending 
largely  on  the  climate,  rainfall,  and  mean  depth.  In  a  good 
reservoir  seepage  losses  should  be  small,  the  principal  loss  being 
from  evaporation.  The  seepage  losses  in  a  reservoir  will,  in  gene- 
ral, increase  with  increasing  depths  of  water.  Annual  evapora- 
tion losses  usually  lie  between  3  and  7  feet,  in  the  arid  West. 

Evaporation  tests  are  usually  conducted  by  immersing  a  vessel 
filled  with  water  in  the  center  of  a  tank  or  reservoir.  In  order 
to  protect  against  waves,  the  immersed  vessel  is  surrounded  by  a 
bulkhead.  Shielding  the  pan  from  the  wind  —  which  is  necessary, 
however  —  will  introduce  an  error  in  the  results,  as  it  is  a  well- 
known  fact  that  evaporation  is  considerably  higher  on  windy 
than  on  still  days,  owing  to  the  more  intimate  contact  between 
water  and  air.  The  surface  area  and  the  mean  depth  of  a 
reservoir,  as  well  as  protection  of  the  same  from  winds,  have  an 
important  bearing  on  reservoir  efficiency. 

Elements  of  depreciation: 

Reservoirs  which  are  located  in  the  bed  of  a  water  course  are 
liable  to  damage  from  floods  of  special  violence,  and  they  are 
also  subject  to  depreciation  by  the  filling  of  the  reservoir  with 


DIFFERENT   SOURCES   OF    WATER   SUPPLY.          45 

sediment  carried  down  by  the  streams.  Possible  damage, 
owing  to  this,  depends  largely  on  the  average  annual  amount  of 
solid  matter  carried  by  the  streams.  A  reservoir  of  small 
capacity  with  reference  to  the  annual  flow  of  the  stream,  if 
in  the  bed  of  the  stream,  will  be  damaged  by  the  deposit  of 
sediment  to  a  larger  relative  extent  than  a  larger  reservoir 
under  similar  conditions.  In  many  reservoirs  arrangements 
nave  been  made  for  flushing  out  the  sediment,  through  scour- 
ing galleries. 

Cost  of  Stored  Water. 

In  estimating  the  value  of  water  delivered  by  a  reservoir,  due 
attention  should  be  given  to  the  condition  of  the  case,  par- 
ticularly to  the  element  of  depreciation. 

Let  L  =  cost  of  land  for  reservoir, 

i   =  per  cent  interest  and  taxes, 
R  =  cost  of  reservoir  construction, 
P  =  per  cent  fixed  charges  of  reservoir, 
A  =  annual  cost  of  attendance, 
W  =  cost  of  water  supplied  to  reservoir, 
Y  =  acre-feet  of  water  supplied  to  reservoir. 
E  =  reservoir  efficiency. 

Cost  of  stored  water  W  +  Li  +  RP  +  A  =  X. 

X 

Cost  of  stored  water  per  acre-foot  =  -r      • 


Value  of  Location. 

Usually  the  location  of  a  natural  reservoir  is  not  a  matter  of 
choice,  as  it  is  dependent  mainly  upon  the  lay  of  the  land. 
However,  if  it  is  possible  to  choose  locations,  the  three  following 
cases  should  be  considered: 

1.    Reservoir  in  bed  of  stream. 

Advantages:  (a)  It  is  not  necessary  to  use  a  canal,  or  to 
construct  means  of  diversion  of  river  water. 

(6)  The  entire  supply  of  the  river  flows  into  the  reservoir. 

Disadvantages:  (a)  The  reservoir  being  located  in  the  bed 
of  the  stream,  ample  spillway  must  be  provided. 

(6)  Unless  the  dam  is  made  of  masonry  or  other  material 


46  PRACTICAL  IRRIGATION. 

capable  of  serving  as  a  spillway,  it  must  be  constructed  to  a 
sufficient  height  above  the  spillway  to  provide  necessary  safety. 

(c)  Possible  damage  by  flood  water. 

(d)  Sedimentation  of  reservoir. 

(e)  Owing  to  conditions  encountered,  it  may  be  necessary  to 
build  expensive  masonry  dams. 

2.  Reservoirs  near  the  source  of  supply  not  located  directly 
in  the  river  channel. 

Advantages:  (a)  Reservoirs  not  subject  to  damage  from  ex- 
cessive floods.  Water  supplied  may  be  more  easily  controlled. 

(6)  Owing  to  this  they  allow  of  cheaper  construction  than 
reservoirs  of  the  first  class,  since  banks  need  not  be  built  to 
such  excessive  height,  and  a  smaller  spillway  will  suffice. 

(c)  Sand  traps  may  be  provided  in  the  supply  ditch,  thus 
keeping  part  of  the  sediment  from  entering  the  reservoir. 

Disadvantages:  (a)  Diverting  works  and  a  canal  must  be 
built. 

(b)  In  the  event  of  a  considerable  rise  in  the  stream  from  which 
the  water  supply  is  derived,  water  which  in  the  first  case  could 
be  stored  were  the  reservoir  not  full,  might  in  the  second  case 
be  lost,  owing  to  inability  of  the  canal  to  carry  the  same. 

3.  Reservoirs  located  near  the  point  of  use  of  water. 
Reservoirs  of  this  description  would  have  the  advantage  over 

reservoirs  of  the  last-mentioned  type,  that  a  smaller  capacity 
would  serve  the  purpose,  since  it  would  be  unnecessary  to  provide 
reservoir  capacity  to  supply  seepage  loss  of  ditches  necessary 
for  class  No.  2.  On  the  other  hand,  they  would  necessitate 
the  construction  of  larger  ditches  for  conveying  the  water  than 
would  be  necessary  in  case  2,  since,  aside  from  other  considera- 
tions, the  ditches  in  this  case  must  carry  sufficient  water  to 
allow  for  reservoir  seepage  and  evaporation,  and  it  would  be 
advisable  to  provide  ditches  of  sufficient  size  to  carry  water, 
much  of  which  might  otherwise  be  lost. 

In  many  parts  of  the  country  no  natural  reservoir  sites  are 
available.  In  this  event,  to  store  water  requires  the  construction 
of  an  artificial  storage  reservoir. 

Except  for  very  small  capacities,  the  only  practical  form  of 
reservoir  consists  of  an  earth  tank  or  reservoir,  usually  con- 
structed by  throwing  up  banks  to  surround  the  same.  Artificial 
reservoirs  perform  a  most  useful  service  in  many  cases,  and 


DIFFERENT   SOURCES   OF    WATER   SUPPLY.          47 

investigations  show  that  they  may  be  extended  in  many  places 
to  the  storage  of  large  quantities  of  water  on  a  commercially 
profitable  basis,  indeed  at  an  average  cost  less  than  the  average 
cost  of  natural  reservoirs. 

Artificial  Reservoirs. 

Artificial  reservoirs  may  be  divided  into  two  classes:  (1)  Those 
of  small  capacity,  and  (2)  those  of  large  capacity.  A  reservoir 
of  small  capacity  is  one  that  will  store  the  discharge  of  a  well 
pump  or  small  stream  for  from  half  a  day  to  a  week,  whereas 
reservoirs  of  large  capacity  will  serve  to  store  water  for  a 
considerable  period.  Small-capacity  reservoirs  are  used  par- 
ticularly as  a  storage  for  pumped  water  or  artesian-well  water, 
and  will  serve  the  following  purposes:  (1)  They  will  permit  a 
continuous  24-hour  operation  of  pumping  plants  or  flow  of 
wells  without  night  irrigation,  storing  water  during  the  night 
and  irrigating  with  it  during  the  day.  (2)  They  will  allow 
the  use  of  irrigation  heads  larger  than  the  rate  of  the  supply  to 
the  reservoir,  thus  reducing  the  percentage  of  seepage  losses 
in  the  distributing  ditches.  (3)  The  quantity  of  water  which 
one  man  is  capable  of  handling  may  be  more  easily  supplied 
in  this  manner,  thus  reducing  the  cost  of  labor  for  irrigation. 
(4)  They  allow  the  operation  of  a  pumping  plant  under  full 
capacity  and  hence  under  conditions  of  highest  efficiency  at  all 
times.  Therefore,  they  may  be  a  source  of  considerable  saving 
in  both  fuel  and  labor  charges.  For  example,  if  it  is  desired 
to  irrigate  a  certain  field,  and  only  one-half  the  flow  of  the  pump 
can  be  used  to  advantage,  this  water  can  be  supplied  either 
from  what  is  stored  in  the  reservoir  without  starting  up  the 
pump,  or  else  the  pump  can  be  operated  at  its  full  capacity, 
delivering  the  water  that  is  required  to  irrigate  the  field,  and 
storing  the  remainder  in  the  reservoir.  (5)  A  small  plant  with 
reservoir  may  be  installed  to  operate  continuously  in  place  of 
the  installation  of  a  larger  plant  operating  only  a  portion  of  the 
time,  thus  cutting  down  the  first  cost  of  the  plant,  but  increasing 
the  cost  of  labor,  in  case  it  should  be  necessary  to  have  an 
attendant  always  on  hand.  Small  gasoline  plants  require  very 
little  attendance,  and  would  benefit  particularly  in  this  event. 
This  decrease  in  the  capacity  of  the  pump  may  have  a  very 


48  PRACTICAL  IRRIGATION. 

important  bearing  on  the  fuel  consumption  in  case  the  supply 
is  derived  from  a  well,  due  to  the  decreased  head  against  which 
the  water  must  be  elevated.  This  head  may  be  expressed  by 
the  formula  H  =  A  +  BQ  +  CQ2  (see  page  86).  Take,  for 
instance,  a  case  which  came  within  the  observation  of  the  writer, 
where  water  was  pumped  from  a  well,  the  water  level  being  2  feet 
below  the  level  of  the  ground.  The  water  was  hardly  throttled 
at  all  in  the  ground  itself,  practically  all  the  head  against  which 
the  pump  had  to  operate  being  caused  by  friction  in  the  well 
casing.  As  the  plant  was  run  the  pump  had  to  operate  against 
a  head  of  50  feet.  The  pump  station  was  run  only  during  the 
day.  Providing  the  station  had  been  operated  all  the  day, 
delivering  one-half  the  previous  quantity  of  water,  it  would 
have  required  practically  a  head  one-fourth  of  that  which  it  did 
require,  thus  necessitating  a  power  plant  only  one-eighth  of  the 
size,  and  reducing  very  materially  both  the  first  cost  of  the 
plant  and  the  running  expenses,  although  the  cost  of  labor  would 
have  been  increased.  The  saving  in  fuel,  however,  would  have 
far  more  than  compensated  for  the  additional  labor,  not  to 
mention  the  saving  in  fixed  expenses. 

Considerations  which  can  be  urged  against  reservoir  construc- 
tion are:  (1)  First  cost.  (2)  The  land  occupied.  (3)  Addi- 
tional height  to  which  water  must  be  raised  in  order  to  fill  the 
reservoir.  (4)  Seepage  and  evaporation.  If  the  material  for 
the  construction  of  the  reservoir  is  at  all  suitable,  proper  con- 
struction should  largely  eliminate  seepage.  With  small  reser- 
voirs, seepage  and  evaporation  should  be  of  little  importance. 
While  all  stages  of  reservoirs  of  intermediate  capacity  may  be 
built,  yet  in  general  the  most  useful  sizes  would  be  reservoirs 
holding  from  12  hours  to  a  week's  pump  or  well  capacity,  or 
else  reservoirs  of  large  size  retaining  the  water  for  long  periods 
except  where  the  supply  is  pumped  by  windmills,  and  hence  has 
to  depend  on  an  uncertain  source  of  power. 

Canals  as  Storage  Basins. 

It  is  frequently  necessary  to  supply  from  pumping  plants  a 
flow  of  water  considerably  less  than  the  normal  supply  of  the 
pumps.  In  cases  of  this  nature  the  storage  of  water  pumped  is 
a  very  useful  feature.  In  some  cases  canals  have  been  made 


D1F1-'KIIK\'T    SOrnCES    OF    WATER    SUPPLY.          49 

sufficiently  large  to  answer  this  purpose.  However,  generally 
speaking,  the  use  of  a  canal  for  a  storage  basin  is  not  to  be  looked 
on  with  favor,  for  the  following  reasons:  (1)  In  proportion  to  the 
volume  stored  it  presents  a  large  surface  for  seepage.  (2)  In  com- 
parison with  a  reservoir  proper,  the  bank  is  much  longer  than 
the  corresponding  reservoir  bank,  and  usually  not  so  strongly 
built.  A  break  in  the  canal  bank  where  a  large  amount  of  water 
is  stored  is  liable  to  do  considerable  damage  to  adjoining  land. 
(3)  In  comparison  with  reservoirs  of  equal  storage  capacity, 
the  cost  of  the  canal  banks  would  be  excessive  as  compared 
with  cost  of  reservoir  bank.  (4)  To  avoid  unnecessary  waste 
of  water  and  loss  of  time  in  reaching  the  lands  to  be  irrigated, 
it  is  desirable  that  canals  should  not  have  too  large  capacity. 
In  places  where  canals  are  used  as  storage  basins,  the  construc- 
tion is  usually  of  such  a  nature  that  in  order  to  raise^the  water 
to  sufficient  height  to  irrigate  certain  sections  of  the  field  the 
canal  must  be  filled  completely.  Where  storage  basins  are 
desired  it  would  be  decidedly  preferable  to  construct  reservoirs 
for  such  purpose,  and  to  build  the  canals  of  sufficient  capacity 
to  convey  the  water  to  the  land  without  velocity  sufficiently 
great  to  erode  the  banks.  They  should,  however,  be  built  with 
banks  sufficiently  strong,  which  should  be  at  a  safe  elevation 
above  high- water  mark  in  the  canal.  Any  amount  of  trouble 
and  annoyance  in  irrigation  is  caused  by  flimsily  constructed 
canal  banks  when  the  water  is  run  dangerously  close  to  the  top 
and  is  constantly  breaking  through. 

Underground  Supply. 

Perhaps  the  greatest  number  of  irrigation  plants  derive  their 
water  from  the  underground  water  supply  by  means  of  wells. 
The  underground  supply  has  the  very  important  advantage 
that  it  can  be  tapped  usually  at  the  point  of  use,  thus  doing 
away  with  the  necessity  of  long  conduits  with  their  inevitable 
losses  and  high  cost. 

The  earth  is  composed  of  various  strata  which  usually  form 
planes  more  or  less  continuous  over  large  areas.  These  strata 
may  be  classified  with  reference  to  the  resistance  they  offer 
to  the  passage  of  water,  some  of  them  transmitting  water  readily, 
while  others  are  quite  impervious.  The  underground  waters 


50-  PRACTICAL  IRRIGATION. 

flow  through  certain  strata  or  channels.  It  is  the  exception, 
however,  when  they  flow  in  open  subterranean  channels,  by  far 
the  greatest  part  of  the  flow  being  through  porous  strata  of 
sand,  sandstone,  or  gravel.  The  resistance  to  flow  through  the 
water  strata  is  so  great  that  the  movement  is  usually  very 
gradual,  and  the  flow,  instead  of  being  confined  in  a  small  channel, 
often  fills  the  entire  stratum.  The  formation  of  the  earth  is  such 
that  the  ground  is  divided  into  water  strata  which  are  more  or 
less  independent  of  each  other,  depending  on  the  imperviousness 
of  the  intervening  strata.  Each  water  stratum  receives  the 
seepage  into  the  catchment  area  of  the  stratum,  or  from  direct 
connection  with  or  leakage  from  other  strata.  Fig.  2  illustrates 
the  general  principle  of  water  distribution  into  various  strata, 
the  figure  representing  a  profile  and  section  of  the  land;  the 


Figs.  2  and  3.     Water  Distribution  in  Strata. 

various  water  strata,  a,  6,  and  c,  being  fed  respectively  from 
the  surface  seepage  from  A,  B,  and  C  alone,  provided  the  inter- 
vening strata  are  impervious.  If  the  flow  of  water  in  a  water- 
bearing stratum  is  sufficiently  great  just  to  saturate  the  entire 
stratum  at  any  point,  then  if  this  stratum  be  tapped  by  a  well 
the  water  will  rise  in  the  well  to  the  level  of  the  top  of  the 
stratum.  Should  the  flow  increase,  water  will  be  under  pres- 
sure in  the  stratum,  and  will  rise  in  the  well  to  a  higher  level. 
Should  the  pressure  be  sufficiently  great  to  raise  the  water  above 
the  ground  level,  the  well,  if  an  opening  be  made  in  its  casing 
at  the  ground,  will  give  forth  an  artesian  flow. 

It  is,  of  course,  not  necessary  to  have  a  flow  through  the 
ground  strata  for  the  water  level  to  be  raised  to  a  sufficient 
height  to  be  under  pressure,  as  is  seen  in  Fig.  3. 

The  water-bearing  strata  of  the  earth  form  natural  reservoirs 
of  vast  extent.  Sandy  soils  will  contain  from  25  to  40  per  cent 
of  their  total  volume  in  storage  capacity,  and  in  consideration  of 
their  enormous  extent  it  is  evident  that  the  underground 
storage  reservoirs  are  of  far  greater  extent  than  all  the  surface 


DIFFERENT   SOURCES    OF    WATER    SUPPLY.  51 

rosorvoirs  which  will  ever  be  constructed.  The  underground 
water  comes  directly  from  seepage  through  the  surface  of  the 
soil.  The  rainfall  and  seepage  from  rivers  and  canals  and  from 
irrigated  land  are  the  main  sources  of  its  supply.  Unlike  the 
surface  storage  reservoirs,  the  greater  part  of  the  underground 
water  is  in  continual  motion,  but  the  retarding  effect  of  the  soil 
is  so  great  that  it  forms  a  strong  tendency  to  equalize  the  flow. 
The  seepage  through  the  soil  forms  an  important  source  of 
supply  of  most  rivers,  reappearing  in  the  form  of  springs,  and 
in  some  places  coming  out  under  the  ocean. 

The  rate  of  movement  of  underground  waters  varies  directly 
with  the  head  or  pressure  causing  the  flow  in  a  given  distance. 
The  nature  of  the  soil  has  also  a  most  important  effect  on  the 
flow.  The  more  open  the  soil,  the  greater  the  flow;  while  the 
finer  the  grains  of  the  soil,  the  less  the  flow.  Gravel  transmits 
water  readily,  coarse  sand  fairly  well,  fine  sand  slowly,  while 
sand  with  clay  in  it  offers  a  great  resistance  to  the  flow  of  water. 
In  limestone  formations  the  water  is  often  found  in  caverns  in 
the  rock,  frequently  flowing  as  a  subterranean  river.  In  general, 
the  more  free  the  nature  of  the  water-bearing  strata,  the  greater 
is  the  likelihood  of  obtaining  large  supplies  therefrom,  while 
from  poor  strata  the  supply  is  likely  to  be  much  restricted. 
The  source  and  extent  of  the  water  which  goes  to  make  up  the 
underground  supply  should  be  carefully  considered  before 
attempting  extensive  development.  The  seepage  into  a  stratum 
is  dependent  on  the  catchment  area  of  that  stratum,  the  rainfall, 
evaporation  and  surface  run-off  of  the  land.  Return  seepage 
from  irrigated  lands  may  form  an  important  addition  to  the 
underground  supply,  as  is  evidenced  by  the  return  seepage  to  the 
North  Platte  River  from  the  irrigated  lands  near  by.  This  is 
described  at  length  in  bulletin  No.  157  of  the  Office  of  Experi- 
ment Stations  of  the  United  States  Department  of  Agriculture. 

The  subject  of  the  flow  of  underground  water  is  treated  at 
length  by  Professor  Slichter  in  investigations  of  the  United 
States  Geological  Survey.  The  resistance  of  a  porous  medium 
to  the  flow  of  water  is  dependent  on  the  size  of  grains  and  on 
their  arrangement.  The  larger  the  grains,  the  less  the  resistance. 
If,  however,  large  and  small  grains  be  mixed  together,  the  small 
grains  will  fill  the  spaces  between  the  large  grains,  causing  the 
resistance  to  increase  much  beyond  that  of  sand  having  grains 


52 


PRACTICAL  IRRIGATION. 


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DIFFERENT   SOURCES    OF    WATER   SUPPLY.          53 


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54 


PRACTICAL  IRRIGATION. 


of  the  average  size.  The  result  of  such  a  mixture  will  cause  the 
resistance  to  be  equal  to  the  resistance  of  a  sand  with  uniform 
grains  still  smaller  in  size.  The  size  grains  giving  the  equivalent 
effect  is  known  as  the  effective  size. 

Measurements  on  the  resistance  of  sand  to  flow  are  usually 
made  in  the  laboratory  by  what  is  known  as  the  aspirator. 
The  sand  is  first  dried,  and  then  air  is  forced  through  a  standard 
sized  tube  of  sand.  From  the  relation  between  the  pressure  of 
air  and  the  flow,  the  resistance  to  the  flow  of  water  can  be 
deduced. 

Table  XVII,  taken  from  Water  Supply  and  Irrigation  Paper 
No.  140  by  the  United  States  Geological  Survey  by  Charles  S. 
Schlichter,  gives  information  as  to  the  pressure  necessary  to 
force  water  through  soils  with  various  size  grains. 


Temperature 
r  • 

Relative  flow 
Per  cent 

Temperature 

Relative  flow 
Per  cent 

32 

0.64 

70 

1.15 

35 

0.67 

75 

1  .23 

40 

0.73 

80 

1  .30 

45 

0.80 

85 

1.39 

50 

0.86 

90 

1.47 

55 

0.93 

95 

1.55 

60 

1.00 

100 

1  .64 

65 

1  .08 

It  is  to  be  noted  that  the  resistance  to  flow  varies  greatly 
with  the  temperature.  The  porosity  given  in  the  table  repre- 
sents the  percentage  of  void  space  in  the  sand,  and  the  figures 
show  that  the  arrangement  of  sand  grains  has  a  most  important 
effect  on  the  transmission  of  water.  If  the  sand  is  tightly  packed 
it  will  offer  a  far  higher  resistance  to  flow  than  that  of  loosely 
packed  sand  of  the  same  effective  size  of  grain. 

The  transmission  constant  given  in  the  table  represents  the 
cubic  feet  of  water  per  minute  which  a  column  of  sand,  1  foot 
square  and  1  foot  long,  will  transmit  under  a  difference  of  head 
at  the  ends  of  1  foot  of  water. 


CHAPTER  VII. 
METHODS    AND    APPLIANCES    FOR    OBTAINING    WATER. 

HAVING  decided  on  the  source  of  supply  and  the  quantity 
of  water,  the  next  question  which  confronts  the  irrigator  is  how 
will  he  be  able  to  obtain  the  water  in  a  position  where  he  can 
utilize  it  on  the  land,  and  what  structures  will  be  needed  for 
the  work.  The  water  must  be  delivered  at  a  place  or  places 
sufficiently  high  to  irrigate  all  the  land  by  gravity.  In  a  very 
limited  number  of  cases,  water  is  delivered  under  pressure  and 
distributed  by  a  piping  system,  but,  as  a  general  rule,  water  is 
distributed  by  gravity  alone. 

Conduction   and  Distribution  of  Water. 

Having  selected  the  location  where  the  water  is  to  be  delivered, 
the  next  problem  is  how  to  get  it  there.  For  obtaining  water 
from  streams  or  reservoirs,  the  structure  most  commonly  em- 
ployed is  the  canal.  The  usual  method  of  constructing  a  canal 
is  by  excavation,  the  dirt  which  is  thrown  out  forming  part  of 
the  bank.  The  water  level  is  usually  not  run  higher  than  the 
natural  surface  of  the  ground  before  excavation,  but  if  it  is 
desired  to  use  the  artificial  banks  for  holding  water,  they  must 
be  made  comparatively  water  tight,  and  after  vegetation  has 
been  removed,  the  ground  at  the  banks  should  be  plowed  to 
insure  a  union  between  the  old  and  the  new  ground.  Sometimes 
the  entire  banks  are  constructed  artificially,  but  it  is  usually 
desirable  to  have  the  water-carrying  part  of  the  canal  in  the 
natural  ground.  The  water  in  a  canal  should  not  be  run  too 
close  to  the  top,  but  a  safe  margin  should  be  allowed  to  provide 
for  the  inevitable  variations  in  water  surface  and  the  effect  of 
wind.  Where  the  canal  runs  through  porous  strata,  it  should 
be  lined  to  prevent  serious  seepage  losses.  The  materials 
usually  employed  for  such  a  purpose  are  cement,  clay, 
or  puddle,  which  is  a  mixture  of  clay,  gravel,  and  sand.  Cement 

65 


CF  THE 


56  PRACTICAL  IRRIGATION. 

is  usually  the  most  expensive  lining,  but  will  practically  prevent 
seepage  loss.  Before  lining  with  cement,  the  sides  and  bottom 
should  be  thoroughly  compacted  to  obviate  settlement  and 
cracking.  Canal  banks  should  not  be  run  to  a  point  on  top,  but 
a  safe  width  of  bank  should  be  allowed.  Also  the  slope  of  the 
banks  should  not  be  so  great  as  to  cause  danger  of  caving.  In 
the  best  construction  the  canal  linings  are  constructed  with 
rock  or  concrete,  which  is  then  covered  with  a  cement  mortar; 
but  in  some  cases  where  the  banks  are  sufficiently  firm,  the 
cement  mortar  is  directly  applied  thereto.  The  cross-section 
of  the  canal  should  be  sufficient  to  carry  the  water  without  too 
high  a  velocity.  In  earth  the  best  velocity  is  between  2  and  2.5 
ft.  per  sec.  A  higher  velocity  is  apt  to  erode  the  banks,  and  a 
lower  velocity  will  allow  the  deposition  of  sediment  and  the 
growth  of  weeds  and  vegetation  which  must  subsequently  be 
removed.  The  velocity  of  water  in  a  canal  is  dependent  on  the 
wetted  surface,  the  cross  section  of  the  water,  the  slope  of  the 
canal,  and  the  nature  of  the  material  composing  the  banks. 

In  a  given  case  where  the  section  and  wetted  surface  are 
determined,  the  desired  velocity  may  be  obtained  by  running 
the  canal  on  the  proper  slope.  The  bottom  of  a  canal  should 
be  run  on  a  uniform  slope  determined  accordingly. 

The  line  of  the  canal  should  be  laid  out  running  back  from  the 
point  at  which  water  is  to  be  delivered,  to  the  source  of  supply, 
by  the  shortest  and  most  practical  route;  the  line  rising  in  ele- 
vation according  to  the  determined  slope,  and  avoiding,  wherever 
possible,  cuts  or  depressions. 

In  case  a  steeper  grade  than  that  selected  is  desirable,  to 
shorten  the  route  or  for  other  purposes,  the  additional  fall  in 
the  canal  must  be  taken  care  of  in  order  not  to  cause  too  high 
velocities.  The  usual  method  of  accomplishing  this  result  is 
by  the  use  of  drops.  In  this  way  small  artificial  falls  are 
inserted  in  the  canal  for  stepping  down  from  one  level  to 
another.  The  canal  is  then  run  on  the  desired  grade.  The 
drops  are  usually  provided  with  adjustable  flashboards  for 
varying  the  level  of  the  water  in  the  different  sections  of  canal, 
or  for  preventing  the  water  from  flowing  past  the  sections 
where  it  is  desired  to  be  used.  The  drops  are  constructed 
with  a  foundation  for  taking  care  of  the  impact  of  the  falling 
water  and  preventing  erosion.  Where  made  of  timber  and 


METHODS    FOR    OBTAINING    WATER. 


57 


located  on  alluvial  soil,  they  are  frequently  constructed  by 
driving  two  rows  of  sheet  piling  across  the  canal.  Stringers 
are  attached  to  the  top  of  the  same,  on  which  a  flooring  is 
run,  the  level  of  the  flooring  being  even  with  the  bottom  of 
the  outgoing  canal.  On  the  flooring  is  constructed  a  frame- 
work supporting  sheet  boarding  run  across  the  canal,  either 
in  a  vertical  plane,  or  with  the  upper  side  inclined  down 
stream.  This  is  provided  with  a  superstructure  and  removable 
flashboards,  and  wings  are  carried  well  into  each  bank  to  pre- 


Fig.  4.     Timber  Drops  on  Soft  Soil. 

vent  the  structure  from  washing  out.    The  impact  of  the  falling 
water  is  taken  on  the  timber  flooring  (see  Fig.  4). 

Where  it  is  necessary  to  carry  the  water  across  draws  or 
depressions,  it  may  be  accomplished  by  any  of  the  following 
methods: 

1.  Flume. 

2.  Earth  embankment. 

3.  Inverted  siphon. 

Flumes  are  usually  constructed  of  timber,  and  are  used  also 
for  conveying  the  water  where  the  ground  is  treacherous  and 
liable  to  excessive  seepage,  as  well  as  in  places  where  ditch  con- 
struction is  expensive  or  impractical,  such  as  along  vertical 
cliffs,  etc. 

Wooden  flumes  should  always  be  kept  wet  where  practicable, 
since  alternate  wetting  and  drying  of  the  timber  leads  to  rotting 
of  the  wood,  distortion  and  shrinkage,  and  consequent  leaks. 
The  life  of  wooden  flumes  where  not  kept  filled  with  water  is  of 
necessity  short,  but  often  wood  is  the  only  available  material. 
Concrete,  and  particularly  reinforced  concrete,  while  higher  in 


58 


PRACTICAL  IRRIGATION. 


first  cost  than  timber,  will  often  give  far  more  desirable  struc- 
tures, with  a  much  smaller  cost  for  maintenance.  The  use  of 
concrete  for  such  purposes  is  increasing,  as  its  advantages  are 
better  appreciated,  but  often  the  financial  condition  of  irri- 
gation companies  when  first  organized,  will  not  allow  the  use 
of  more  expensive  types  of  construction.  For  carrying  the 
flume  across  depressions,  wooden  trestles  and  supports  are 
commonly  used,  though  sometimes  steel  is  used  for  this  purpose. 
The  flume  must  be  carried  on  suitable  grade  to  discharge  the 
desired  quantity  of  water.  The  velocities  employed  in  flumes 
are  considerably  higher  than  are  used  in  earth  ditches,  usually 
varying  from  5  to  10  ft.  per  sec.  They  are  limited  only  by  the 
available  head  and  by  the  erosive  action  of  water  on  the 
material  of  the  flume.  The  higher  the  velocity,  the  smaller  and 
cheaper  the  flume.  The  change  of  velocity  in  going  from  the 
ditch  to  the  flume  and  vice  versa,  should  be  made  gradually 
by  tapering  the  entrance  to  the  flume  and  the  discharge  there- 
from, and  all  the  structures  at  entrance  and  exit  must  extend 
sufficiently  far  not  to  allow  the  higher  velocities  to  act  on 
materials  liable  to  erosion. 

Wooden  flumes  are  usually  constructed  of  timber,  the  bottom 
and  sides  being  tongue-and-groove  or  ship-lapped  to  make  them 


Fig.  5.     Wooden  Flume  Construction. 

tight.  Where  the  sides  and  bottom  join,  a  triangular  batten  is 
nailed  to  the  inside,  and  the  joints  covered  with' pitch  or  asphalt 
to  make  them  hold  water  (see  Fig.  5). 

Where  earth  embankments  are  used  to  carry  the  water  across 
depressions,  there  will  be  at  first  considerable  settlement  and 
leakage  until  the  material  is  finally  compacted. 

Where  cement  or  concrete  lining  is  used  for  carrying  the 
water  over  such  embankments,  the  latter  should  first  be 
thoroughly  compacted  before  the  lining  or  conduit  is  put  in 
place.  If  the  embankment  is  across  a  draw,  provision  must  be 


METHODS    FOR    OBTAIXING    WATER. 


59 


made  for  carrying  off  the  rain  water  which  discharges  into  the 
draw,  by  suitable  culverts  or  conduits  under  the  embankment. 
Inverted  siphons  are  commonly  used  for  conveying  the  water 
across  depressions.  An  inverted  siphon  consists  of  a  pipe  or 
pipes  or  a  closed  conduit,  with  suitable  intake  and  outlet,  where 
the  intake  and  outlet  are  higher  than  other  parts  of  the  pipe, 
and  consequently  the  remainder  of  the  pipe  is  under  pressure. 
The  discharge  end  must  be  placed  at  an  elevation  sufficiently 
below  the  entrance,  for  the  difference  in  elevations  to  over- 
come the  friction  losses  in  flowing  through  the  pipe.  Velocities 
of  6  to  10  ft.  per  sec.  are  commonly  used  for  such  work.  The 
intake  and  outlet  should  be  so  constructed  as  to  give  a  gradual 
change  in  the  velocities  of  the  water  between  canal  and  siphon. 


TABLE  XVIII. 
THE    APPROXIMATE   COST  OF   REDWOOD   PIPE  IN   CALIFORNIA. 


Inside 

Cost  of  pipe  per  foot  for  heads 

diam.of  pipe, 

For  each 

mcnes 

Oto20 

20  to  30 

30  to  40 

40  to  50 

additional  10 

feet  head 

12 

$0.38 

$0.40 

$0.42 

$0  .4.-, 

$0  .03J 

14 

.44 

.46 

.48 

.  .51 

.04 

16 

.52 

.54 

.57 

.60 

.04* 

18 

.57 

.60 

.63 

.66 

.05 

24 

.98 

1  .02 

1  .06 

1  .11 

.07J 

30 

1  .24 

1.29 

1.34 

1.40 

.09 

36 

1  .46 

1.53 

1.60 

1  .68 

.12 

48 

1  .95 

2.08 

2.22 

2.36 

.18 

60 

3.73 

3.96 

4.19 

4.43 

.35 

72 

4.57' 

4.90 

5.23 

5  .57 

.41 

84 

6.85 

7.31 

7.78 

8.25 

.64 

96 

8.00 

8.56 

9.17 

9.70 

.80 

108 
120 

9.00 
10.30 

9.88 
11  .15 

10.76 
12.00 

11  .65 
12.85 

1.06 
1.17 

Where  distances  and  pressures  are  small,  such  as  for  crossing 
under  a  road,  wooden  boxes  are  frequently  used.  The  materials 
generally  utilized  for  conduits  are  riveted  steel  pipe,  wooden 
pipe,  or  reinforced  concrete  pipe.  The  two  latter  are  usually 
employed  only  in  large  sizes.  Wooden  pipe  is  constructed  of 
staves  running  longitudinally,  which  are  bound  together  by 


60  PRACTICAL  IRRIGATION. 

round  iron  bands,  provided  with  adjustable  nuts  for  tightening 
them.  Where  the  end  joints  occur,  sheet-steel  tongues  are 
inserted  to  make  them  water  tight,  but  the  longitudinal  joints 
are  kept  tight  by  the  pressure  exerted  by  the  bands. 

Wooden  pipe  when  properly  installed  is  subject  to  very  little 
depreciation.  It  should  be  set  in  such  a  manner  that  the 
entire  inner  surface  will  always  be  kept  wet.  Manufacturers  of 
wooden  pipe  claim  that  redwood  pipe  under  good  conditions 
should  last  fifty  years,  and  even  under  quite  unfavorable  con- 
ditions at  least  twenty-five  years.  This  would  give  an  average 
annual  depreciation  rate  of  3  per  cent.  Pipe  built  of  pine  is 
subject  to  much  more  rapid  depreciation,  its  life  being  approxi- 
mately fifteen  years  under  similar  conditions,  which  would 
signify  a  7  per  cent  depreciation.  Experience  with  wooden 
pipe  leads  to  the  conclusion  that  a  pipe  not  buried  will  last 
longer  than  one  which  is  buried  only  a  few  inches  to  a  foot  below 
the  surface  of  the  ground,  due  to  the  action  of  roots  and  brush 
on  the  wood.  The  life  of  pipe  may  be  much  prolonged  by  bury- 
ing the  top  at  least  5  feet  below  the  surface.  Exposed  wooden 
pipe  is  more  liable  to  damage  by  fire  or  maliciously  inclined 
people  than  were  it  covered  with  earth. 

One  great  advantage  of  wooden  pipe  over  metal  is  the 
increased  carrying  capacity  due  to  the  smoothness  of  the  wood. 
Thus,  for  example,  wooden  pipe  will  carry  approximately  16  per 
cent  more  water  than  the  same  size  iron  pipe  for  a  given  loss  of 
head,  owing  to  the  greatly  diminished  friction. 

Reinforced  concrete  pipe  is  used  in  large  sizes,  the  concrete 
being  usually  from  6  inches  to  10  inches  thick,  depending  on 
the  size  of  pipe.  The  reinforcement  consists  of  either  expanded 
metal  or  plain  iron  bars  bedded  in  the  concrete.  If  bars  are 
used,  they  should  be  run  not  only  around  the  pipe  but  also 
longitudinally.  Fig.  10  shows  the  general  form  of  sections  of 
reinforced  pipe.  Wliere  any  quantity  of  such  pipe  is  to  be  laid, 
the  inside  forms  may  be  made  collapsible  and  pulled  along 
inside  the  pipe,  thus  making  a  material  saving  in  the  cost  of 
construction.  Experience  has  shown  the  value  of  concrete 
pipe  under  low  pressures,  but  experiments  made  under  the 
direction  of  the  Geological  Survey,  under  moderate  and  high 
pressures,  apparently  indicate  that  the  pipe  is  not  all  reliable, 
owing  to  leakage  through  the  concrete.  Possibly  in  practice, 


METHODS    FOR    OBTAINING    WATER. 


61 


the  silt  in  the  water  would  seal  up  such  leaks,  but  this  has  not 
been  demonstrated  as  yet. 

In  conveying  the  water  from  a  stream  to  the  land  to  be  irri- 
gated, the  bottom  of  the  canal  in  general  must  be  on  a  slope  less 
than  the  slope  of  the  river,  in  order  to  elevate  the  water  suffi- 
ciently. For  example,  if  the  stream  slopes  10  feet  in  a  mile,  and 
the  canal  be  run  on  a  slope  of  2  feet  per  mile,  it  will  rise  8  feet 


Fig.  6.     Laying  Wooden  Pipe. 

above  the  water  level  of  the  stream  in  a  mile;  and  if  the  point 
from  which  the  water  is  to  be  distributed  over  the  land  is  16  feet 
above  the  stream  level  at  the  nearest  point,  the  canal  must  be 
two  miles  long  to  where  it  strikes  the  river,  unless  the  level 
of  the  latter  be  raised  by  a  dam  or  weir. 

By  placing  such  a  structure  in  the  river  the  water  level  may 


62  PRACTICAL  IRRIGATION. 

be  raised  and  the  canal  length  shortened.  Such  structures  in 
general  must  allow  the  total  flow  of  the  river  to  pass  over 
them  or  through  suitable  spillways,  without  damage  or  danger. 
They  are  often  provided  with  flashboards  for  raising  the 


Fig.  7.     Laying  Wooden  Pipe. 

water  level  when  desired,  which  are  taken  away  to  allow 
the  flood  waters  to  pass  over  the  crest  with  safety  to  the 
structure  and  without  danger  from  raising  the  water  level 
too  high. 

Water  from  the  stream  is  admitted  to  a  canal  through  a 
suitable   form  of  head  gate,   which  controls  the  flow.      The 


METHODS    FOR    OBTAINING    WATER. 


63 


head  gate  may  consist  of  one  or  more  adjustable  gates  guided 
vertically,  driven  by  a  screw  or  rack  and  pinion,  and  guided  in 
suitable  ways,  or  else  may  be  constructed  in  the  form  of  a  drop, 
with  removable  flashboards  for  controlling  the  quantity  of 
water  admitted  to  the  canal. 


Fig.  8.     Finishing  Wooden  Pipe. 

Gates  are  used  also  to  control  the  division  of  water  and  the 
supply  to  branch  canals  and  to  individual  farmers.  Where 
used  for  the  latter  purpose,  and  where  water  is  furnished  by  a 
ditch  company,  it  is  often  customary  to  provide  them  with  a 
lock  which  will  hold  them  in  any  position,  to  prevent  tampering 


64  PRACTICAL  IRRIGATION. 

with  them,  and  not  to  allow  anyone  to  get  more  than  his  share 
of  water. 

Various  forms  of  waste  gates  are  used  to  dispose  of  the  surplus 
water  from  a  reservoir  or  canal,  consisting  of  actual  gates,  or  of 
a  drop  with  removable  flashboards  over  which  the  water  will 
pass,  if  it  exceeds  a  certain  height,  thus  protecting  the  canal  or 
reservoir  from  the  danger  of  too  much  water. 

Where  there  is  liable  to  be  a  deposit  of  earth  near  the  entrance 
to  a  canal,  a  sluice  gate  is  often  provided  in  order  to  dispose  of 
the  same  by  the  velocity  of  the  water  through  the  gate.  The 


Fig.  9.     Joining  Two  Sections  of  Wooden  Piping. 

sluiceway  is  usually  perpendicular  to  the  entrance  to  the  canal, 
and  the  gate  is  arranged  to  open  from  the  bottom,  thus  making 
a  strong  current  to  carry  away  the  deposits. 

Where  water  carries  a  large  amount  of  sediment,  sand  traps 
are  often  provided,  and  are  commonly  constructed  by  enlarging 
the  section  of  the  canal  greatly,  so  to  cause  a  slow  velocity  and 
give  the  water  an  opportunity  to  deposit  the  sediment  instead 
of  filling  the  ditches  with  it.  The  sediment  is  then  disposed  of 
by  means  of  a  sluice  gate.  In  some  streams  with  an  alluvial 
bottom  it  is  customary  when  the  stream  is  low,  instead  of 
allowing  the  water  to  enter  canals  into  which  it  is  to  be  diverted 


METHODS    FOR    OBTAINING    WATER.  65 

normally  by  means  of  a  weir,  to  run  a  temporary  wing  dam  up 
stream  to  prevent  the  large  seepage  losses  from  the  water 
covering  a  large  area  of  the  bottom  of  the  river. 

In  some  places  dams  are  constructed  of  brush  and  rock,  which, 
while  far  from  water  tight,  will  yet  force  the  water  sufficiently 
high  to  enter  the  canals.  These  structures  serve  their  purpose  as 
long  as  there  is  sufficient  water  in  the  stream. 

At  the  junction  of  two  or  more  canals,  a  division  box  is  usually 
constructed,  for  dividing  the  flow  into  the  various  canals. 
Such  structures  are  commonly  made  of  wood,  and  the  adjustment 


Fig.  10.    Cross-section  of  Reinforced  Concrete  Pipe. 

of  water  flow  is  accomplished  by  means  of  gates.  From  the 
main  canals  the  water  is  led  into  lateral  canals,  from  which  it  is 
distributed  to  the  land  by  the  irrigators. 

Small  ditches  or  canals  are  usually  constructed  by  plowing  the 
land  first  and  then  cleaning  the  dirt  out  by  a  V  or  other  type  of 
scraper,  or  by  other  means,  the  shape  usually  depending  on  the 
type  of  construction  and  instruments  used.  Larger  ditches 
are  usually  built  by  the  use  of  drag  scrapers. 

Calculation  of  the  Flow  of  Water  in  Ditches. 

The  following  formula  gives  V  the  velocity  in  feet  per  second 
of  water  in  ditches. 

V  =  C  \/7s, 

where  r  is  what  is  known  as  the  mean  hydraulic  radius,  i.e.,  the 
quotient  obtained  by  dividing  the  cross-sectional  area  of  the 
water  in  the  ditch,  in  square  feet,  by  the  length  in  feet  of 


66  PRACTICAL  IRRIGATION. 

the  wetted  perimeter  of  the  bottom  and  sides  of  the  ditch;  and 
S  is  the  slope  of  the  ditch.  For  example,  if  the  cross-section 
of  the  water  in  the  ditch  be  given  as  in  Fig.  11,  then 

Area  -  12  X  3  =  36  sq.  ft. 

Wetted  Perimeter        =  18  ft., 
and  r  =  M  =  2. 


^mm^mm^    t 


Fig.  11.     Cross-section  of  Ditch. 

If  the  grade  of  the  ditch  be  1  foot  per  1000  feet,  then 
&  -  ToVo  and  V  =  C  V^I. 

According  to  what  is  known  as  the  Chezy  formula,  the  value 
of  C  is  given  for  various  materials  and  slopes,  but  according  to 
the  formula  of  Kutter,  which  is  generally  accepted  by  engineers, 


n 


Fig.  12.     Cross-section  of  Ditch.  Fig.   13.     Cross-section  of  Ditch. 

where  the  following  values  of  n  are  given  for  various  materials : 

n.  KIND  OF  SURFACE. 

.010 Plain  board  or  smooth  cement. 

.012 Common  board. 

.013 Ashlar  or  good  brick. 

.017 Rubble. 

.025 Earth. 

.030 Earth  with  aquatic  plants. 


METHODS    FOR    OBTAINING    WATER. 


67 


As  an   approximation   sufficiently  close    for  most  practical 
purposes,  this  may  be  written 


42 


C  = 


1  + 


42  n 

Vr 


The  following  figures  give  velocities  and  rates  of  discharge 
for  the  farm  ditches  given  in  Figs.  12  and  13,  corresponding  to 
values  of  n  of  .025. 

FLOW  IN  DITCH  SHOWN  IN  FIG.  12. 


Feet  per  100 
feet  slope 

Feet  per  mile 
slope 

Velocity  feet 
per  second 

Discharge  rate 
cubic  feet 
per  second 

0  .0317 

1.67 

0.556 

2.8 

0.1264 

6.67 

1  .118 

5.6 

0.253 

13.33 

1  .585 

7.9 

0.379 

20.0 

1  .940 

9.7 

FLOW  IN  DITCH   SHOWN  IN  FIG.  13. 


0  .0317 

1.67 

0.764 

18.6 

0.095 

5.00 

1.324 

14.9 

0  .1575 

8.33 

1.704 

19.2 

0.221 

11  .67 

2.020 

22.8 

Measurement  of  Flow  of  Water. 

The  usual  method  of  measuring  the  flow  of  water  for  irrigation 
is  by  means  of  a  weir,  which  consists  of  a  structure  with  a  hori- 
zontal edge  over  which  water  pours.  When  a  weir  is  used  for 
measurement  purposes,  the  plane  with  the  horizontal  edge  is 
vertical  and  the  edge  on  the  inside  is  sharp  and  beveled,  so 
that  the  water  touches  it  only  in  a  line.  Three  forms  of  weirs 
are  commonly  used,  known  as: 

1.  Unsuppressed  weir. 

2.  Suppressed  weir. 

3.  Cippoletti  weir. 


68 


PRACTICAL  IRRIGATION. 


In  the  first  two  the  lateral  edges  of  the  weir  are  vertical, 
while  in  the  last  case  they  are  inclined  to  the  vertical  at  an  angle 
whose  tangent  is  0.25. 

The  unsuppressed  weir  consists  of  a  rectangular  opening  not 
so  wide  as  the  channel  of  approach,  while  the  suppressed  weir 


Fig.  14.     Suppressed  Weir. 

has  an  opening  the  full  width  of  the  channel  (see  Figs.  14,  15, 
and  16). 

In  the  measurement  of  water  by  weirs,  the  width  of  weir  and 
the  height  of  water  over  the  crest   (called  the  head)  must  be 


Fig.  15.     Unsuppressed  Weir. 

known.  Shortly  before  the  water  reaches  the  crest  of  the  weir 
it  begins  to  curve  downwards,  and  the  measurement  should  be 
taken  at  a  point  back  of  the  crest  where  the  water  is  level. 


Fig.  16.     Cippoletti  Weir. 

The  discharge  rate  of  a  weir  in  cubic  feet  per  se3ond  is  given  by 
the  formula 

Q  =  CLH* 
for  suppressed  weirs  and  Cippoletti  weirs,  and 

Q  =  CH*  (L  -  0.2  H) 
for  unsuppressed  weirs. 


METHODS    FOR    OBTAINING    WATER. 


69 


In  the  latter  the  width  of  discharge  water  is  restricted  by  the 
tendency  to  crowd  from  the  sides.  This  restriction,  which  is 
dependent  on  the  head  over  the  weir,  is  equivalent  to  shortening 
the  length  of  weir.  The  divergence  of  the  sides  of  the  Cippo- 
letti  weir  is  just  sufficient  to  overcome  the  effect  of  crowding. 
In  the  above  formula?, 

L  =  Length  of  weir  in  feet, 

H  =  Head  over  crest  in  feet,  and 

C  =  A  constant. 

With  the  Cippoletti  weir,  L  =  length  of  bottom  of  weir  in 
feet.  The  value  of  C  is  usually  taken  as  3.33. 

The  bottom  of  the  approach  to  the  weir  should  be  at  a  dis- 
tance below  the  crest  equal  to  at  least  twrice  the  head  on  the 
weir,  and  the  approach  of  water  thereto  should  be  even  and 
uniform  to  insure  accurate  measurements. 

If  this  is  not  the  case,  the  formulae  must  be  corrected  for  the 
velocity  of  approach.  (See  Merriman's  "  Hydraulics.") 

The  tail  water  below  the  weir  should  be  sufficiently  below 
the  crest  of  the  weir  not  to  interfere  with  the  discharge.  The 
following  table  gives  discharges  from  suppressed  or  from  Cippo- 
letti weirs  for  various  heads  per  foot  width  of  weir. 

TABLE   XIX. 
WEIR  TABLE. 


Ft.  head 

Cu.  ft.  per  sec. 

Ft.  head 

Cu.  ft.  per  sec. 

0.10 

0.105 

0.5 

1.177 

0.15 

0.193 

0.6 

1.548 

0.20 

0.298 

0.7 

1.950 

0.25 

0.416 

0.8 

2.383 

0.30 

0.547 

0.9 

2.843 

0.35 

0.690 

1.0 

3.330 

0.4 

0.842 

In  order  to  be  able  to  use  a  weir  measurement,  we  must  be 
able  to  allow  the  necessary  drop.  Where  this  is  not  possible, 
rating  flumes  are  sometimes  used  for  measuring  the  flow  of  water. 
A  rating  flume  is  constructed  with  a  uniform  section  (often 
rectangular)  of  wood  or  concrete,  located  in  a  ditch,  the  area 


70  PRACTICAL  IRRIGATION. 

being  such  that  the  water  will  have  sufficient  velocity  not  to 
deposit  sediment.  A  vertical  gauge  tells  the  height  of  water, 
and  the  flume  is  calibrated  by  measuring  the  relation  between 
the  flow  and  the  height  of  the  gauge.  To  be  at  all  accurate, 
frequent  calibration  is  required  to  provide  for  changes  in  the 
character  of  the  ditch  due  to  erosion  or  sedimentation,  etc. 
To  give  insured  reliable  results  there  should  be  no  causes  affect- 
ing the  wrater  level  for  a  considerable  distance  below  the  flume. 
Hence  such  a  flume  would  be  unreliable  in  case  much  of  the  water 
were  liable  to  be  diverted  from  the  ditch,  at  all  near  the  flume 
and  below  it. 

The  miner's  inch  is  a  unit  commonly  used,  and  the  flow  of 
water  is  sometimes  measured  by  means  of  an  adjustable  slot 
which  may  be  one  inch  wide  and  of  variable  length.  The 
length  is  altered  until  the  discharge  is  just  sufficient  to  hold  the 
water  4  inches  above  the  center  of  the  slot,  when  the  miner's 
inches  discharged  are  equal  to  the  open  length  of  the  slot. 

The  velocity  of  water  is  measured  by  surface  floats,  by  long 
tube  floats  reaching  nearly  to  the  bottom  of  the  channel,  and 
by  current  meters.  For  a  complete  description  of  the  various 
means  of  measuring  water  in  open  conduits,  the  reader  is 
referred  to  Merriman's  "Hydraulics." 

Natural  Reservoirs. 

The  usual  method  of  building  a  natural  reservoir  consists  in  the 
construction  of  a  dam  or  embankment  across  a  stream  or  water 
course.  If  the  dam  is  liable  to  be  overtopped  by  flood  water,  it  is 
usually  built  of  concrete  or  masonry  in  order  to  stand  up  under 
the  action  of  the  water.  If,  on  the  other  hand,  there  is  no  such 
danger,  cheaper  methods  of  construction  .may  be  used.  The 
first  requisite  for  a  dam  is  a  good  foundation,  under  which  it 
is  impossible  for  the  water  to  leak.  Where  it  is  possible  to  do 
so,  the  foundation  of  the  dam  should  be  carried  down  to  an 
impervious  stratum,  with  which  a  tight  joint  should  be  made. 
The  material  of  the  dam,  or  at  least  part  of  the  same,  should  be 
impervious  to  water.  The  dam  structure  should  be  carried  up 
to  a  safe  height  and  an  ample  spillway  provided  so  that  the 
water  will  not  flow  over  the  dam  unless  the  structure  be  made 
of  sufficient  durability  to  stand  the  consequent  wear. 


METHODS    FQR    OBTAINING    WATER.  71 

The  following  are  the  types  of  dams  commonly  used: 

1.  Masonry  dam. 

2.  Concrete  dam. 

3.  Rock  fill  dam. 
(a)  Timber. 
(6)  Steel. 

4.  Timber  crib  dam. 

5.  Wooden  dam. 

6.  Earth  dam. 

In  each  case  the  spillway  should  be  made  so  as  to  resist  the 
action  of  the  discharge  water,  and  in  all  except  the  first  two 
cases  it  must  be  built  of  a  size  and  at  a  sufficient  distance  below 
the  crest  of  the  dam,  to  take  care  of  the  worst  conditions  of 
flood.  In  figuring  the  amount  of  water  to  be  discharged  by  the 
spillway,  unless  more  definite  data  a're  at  hand,  the  same  may 
be  estimated  from  the  drainage  area,  the  rate  of  rainfall, 
and  the  percentage  run-off  of  the  land,  during  severe  storms. 
The  maximum  discharge  may  also  be  calculated  by  noting  the 
highest  level  of  the  flood-water  and  figuring  the  flow  from 
the  cross-section  and  slope  of  the  ground. 

To  avoid  the  action  of  the  erosion  of  water,  the  spillways  are 
usually  so  made  as  either  to  let  the  water  down  gradually  or  in 
steps,  or  else  the  construction  is  such  that  the  falling  water 
strikes  a  water  cushion  formed  by  the  back  water  in  the  stream 
below  the  dam. 

With  concrete  and  masonry  dams,  usually  a  small  overflow 
will  do  no  damage;  but  if  a  large  quantity  of  water  may  flow 
over  the  crest,  it  is  often  rounded  on  top  and  the  dam  is  so 
curved  on  the  bottom  as  to  change  the  direction  of  the  falling 
water  towards  the  horizontal. 

Masonry  and  Concrete  Dams.  —  It  is  particularly  important 
for  masonry  or  concrete  dams  to  have  a  good  foundation, 
preferably  on  bed  rock.  In  case  this  is  not  obtainable,  rows 
of  sheet  piling  with  suitable  flooring  are  sometimes  used.  Fre- 
quently 4-inch  X  12-inch  timbers  are  used  for  this  purpose. 
One  edge  is  cut  to  a  groove,  and  the  other  edge  dressed  to  enter 
it.  The  timbers  are  beveled  on  the  end  so  as  to  hug  together 
when  driven,  and  the  rows  of  piling  are  run  across  the  bed  of 
the  stream,  and  flooring  nailed  to  stringers  is  then  laid  along 
stream. 


72  PRACTICAL  IRRIGATION. 

Where  the  foundation  is  of  rock,  a  trench  is  usually  cut  in  the 
same,  to  form  a  water-tight  joint  with  the  dam.  For  masonry 
or  concrete  dams  this  is  usually  filled  with  concrete  above  the 
rock  level  and  the  dam  built  around  it.  In  the  calculation  of 
dams  of  this  nature,  there  are  three  ways  of  possible  failure 
which  must  be  figured. 

1.  Crushing  of  the  material  of  the  dam. 

2.  Failure  of  the  dam  by  tension  in  the  masonry. 

3.  Sliding  of  the  dam  on  its  base. 

In  figuring  the  stresses  acting,  the  combination  of  weight  and 
effect  of  water  pressure,  and  also  the  wind  pressure  when  the 
reservoir  is  empty,  must  be  figured.  In  a  properly  designed 
masonry  or  concrete  dam  there  is  no  danger  of  the  dam  over- 
turning, since, -if  the  dam  be  figured  so  that  there  is  no  tension 
in  the  masonry,  the  line  of  resistance  must  be  kept  within  the 
middle  third  of  the  section. 

In  the  construction  of  the  masonry  no  horizontal  courses 
should  be  used,  as  they  would  provide  a  natural  plane  of  cleavage 
for  the  dam  from  the  lateral  water  pressure.  In  addition  to  the 
stresses  mentioned,  in  cold  climates  the  lateral  pressure  of  ice 
must  be  considered,  as  well  as  the  brush  and  logs  which  may 
be  carried  over  the  dam  by  a  flood. 

For  an  extended  discussion  of  dams,  the  reader  is  referred  to 
Schuyler's  "  Reservoirs  for  Irrigation  Water  Power  and  Domestic 
Supply,"  and  to  Wegmann's lt  Design  and  Construction  of  Dams." 

Reinforced  concrete  is  used  in  dam  construction,  and  has 
many  structural  advantages  in  the  more  economical  use  of 
material,  modification  in  design,  and  increased  economy.  The 
steel  in  the  concrete  not  only  allows  tension  stresses  not  per- 
missible with  masonry,  but  also  allows  far  higher  compressive 
stresses  to  be  used,  due  to  the  steel,  insuring  a  more  equal  dis- 
tribution of  compressive  stress  than  would  otherwise  exist. 

Some  masonry  dams  are  built  curved  in  plan,  with  the  water 
pressure  acting  on  the  convex  side.  If  the  abutments  are  solid 
rock,  the  curved  form  acts  like  an  arch,  and  adds  materially  to 
the  strength  of  the  dam;  also  should  any  cracks  tend  to  develop 
on  the  inside,  the  tendence  of  the  water  pressure  is  to  close 
them  up  and  prevent  leaks.  The  curved  dam  is  longer  than  the 
straight  dam,  but  the  additional  strength  allows  a  lighter  con- 
struction to  be  used  with  safety. 


METHODS    FOR    OBTAINING   WATER.  78 

Concrete  cores  are  sometimes  used  in  the  center  of  earth 
dams,  and  not  only  tend  to  make  them  water  tight,  but  add  to 
the  safety  of  the  dam,  particularly  in  event  of  the  possibility 
of  floods  overtopping  the  dam.  The  cores  are  usually  only  a 
few  feet  thick;  and  while  the  construction  would  not  allow  a 
large  overpour,  still  the  resistance  to  damage  or  destruction 
from  the  same  would  be  much  greater  than  where  no  such  pre- 
caution is  used. 

Rock-Fill  Dams.  —  A  rock-fill  dam  consists  of  an  irregular 
mass  of  rock  with  some  kind  of  an  impervious  core  or  covering. 
For  the  latter  purpose  timber  and  also  steel  have  been  used. 
The  timber  is  laid  on  the  inside,  usually  in  a  double  layer  so 
as  to  break  joints,  and  the  joints  are  thoroughly  coated  with 
asphalt,  to  make  them  tight.  Where  steel  is  used,  about 
0.25-inch  plate  is  usually  employed,  and  after  being  riveted 
and  caulked  is  bedded  in  concrete  in  the  center  of  the  dam,  the 
concrete  forming  a  mechanical  protection  and  also  preventing 
rust.  The  steel  or  timber  is  carefully  bedded  at  the  bottom 
of  the  dam  to  form  a  tight  joint.  The  slope  of  the  rock  used 
varies  from  one-half  horizontal  to  one  vertical  up  to  one  and 
one-half  horizontal  to  one  vertical.  Rock-filled  dams  will  not 
allow  any  quantity  of  water  to  pass  over  them  with  safety. 

Timber  Crib  Dams.  —  This  is  a  common  form  of  construction 
where  lumber  is  plentiful,  and  consists  of  a  cribwork  of  logs  which 
is  usually  fastened  at  the  intersections  with  drift  bolts,  and 
which  is  filled  with  rock.  Often  the  back  of  the  dam  is  simply 
filled  with  dirt  and  clay  to  make  it  water  tight.  In  dams  of 
this  nature  the  spillway  is  frequently  built  of  logs,  in  a  series  of 
steps. 

Wooden  Dams.  —  There  are  quite  a  variety  of  forms  of  wooden 
dams  in  use.  Where  they  are  built  on  unstable  ground,  the 
foundation  is  usually  constructed  of  sheet  piling  covered  with  a 
flooring.  A  form  of  dam  or  weir  used  extensively  in  certain 
localities  consists  of  from  two  to  three  rows  of  sheet  piling  with 
flooring,  on  which  is  built  an  inclined  sheet  dam  of  timber, 
braced  to  the  flooring  on  the  down -stream  end.  Where  used 
as  a  weir,  removable  flashboards  are  provided  and  a  walk  is 
built  on  a  superstructure  over  the  weir.  The  superstructure 
is  purposely  made  weak,  so  that  in  case  of  brush  catching  thereon 
and  backing  up  the  river  so  as  to  endanger  the  weir,  the  super- 


T4  PRACTICAL  IRRIGATION. 

structure  will  give  way.  The  overflow  water  runs  over  the 
flashboards  and  falls  on  the  flooring,  protected  by  whatever 
water  cushion  the  back  water  may  afford. 

Earth  Dams.  —  In  building  an  earth  dam,  the  surface  soil 
and  all  vegetable  matter  are  first  removed,  then  the  ground  is 
plowed  to  make  a  tight  joint  with  the  material  which  goes  on 
top.  It  is  customary  to  dig  down  to  an  impervious  stratum 
and  build  at  least  part  of  the  bank  of  impervious  material, 
thoroughly  compacting  it,  as  it  is  built,  but  taking  care  to  form 
no  plane  of  cleavage  through  which  the  water  might  subse- 
quently seep. 

In  many  places  earth  dams  have  been  constructed  by  hydrau- 
licking  the  dirt  into  place,  leading  it  to  the  dam  by  troughs  and 
pipes  at  a  very  low  cost.  Where  water  under  pressure  was  not 
available,  pumps  have  sometimes  been  used  for  this  work. 
Some  form  of  protection  must  usually  be  provided  against 
wave  action  on  the  inside.  Rough  stone  laid  in  place,  known 
as  riprap,  is  commonly  used,  and  timber  is  also  employed  for 
this  purpose. 

Embankments.  —  Earth  tanks  and  artificial  reservoirs  are 
usually  constructed  entirely  in  embankment. 

Many  artificial  reservoirs,  built  of  earth,  are  at  present  in  use 
in  irrigation,  some  of  which  are  supplied  by  windmills,  while 
others  derive  their  supply  from  pumped  water  or  artesian 
wells.  The  reservoirs  generally  are  of  small  size,  though  a  few 
of  considerable  capacity  have  been  built  for  artesian  wells.  As 
a  rule  they  are  quite  successful,  although  in  some  instances 
where  the  soil  is  unfavorable  and  the  construction  poor,  diffi- 
culty has  been  experienced  in  making  them  hold  water. 

A  common  method  of  construction  which  is  frequently  adopted 
for  reservoir  banks,  is  to  plow  down  to  clay  under  the  bank  of 
the  reservoir,  to  make  a  water-tight  joint,  and  to  tamp  the 
bank  thoroughly  during  construction  by  letting  the  teams  make 
the  circle  of  the  reservoir  bank  after  dumping  their  load. 
Sometimes  a  layer  of  clay  is  put  on  the  inside  bank  of  the 
reservoir,  and  in  other  cases  dirt  alone  is  used  in  the  formation 
of  the  banks.  If  clay  is  used,  it  would  be  far  preferable  to 
have  it  in  the  center  of  the  bank,  where  it  will  be  protected  from 
drying  out  or  freezing.  Some  reservoir  banks  constructed  of 
black,  waxy  soil,  answer  all  requirements  for  holding  water. 


METHODS    FOR    OBTAINING    WATER.  75 

Leaky  reservoirs  have  frequently  been  remedied  by  puddling 
and  tamping,  by  driving  stock  around  on  the  inside.  Goats 
or  sheep  answer  particularly  well  for  this  purpose,  as  their  hoofs 
are  so  small  that  they  compact  the  earth  thoroughly. 

The  bottom  of  a  certain  large  reservoir,  for  an  artesian  well, 
with  a  clay  stratum  below  the  ground,  appeared  to  be  porous, 
and  water  went  through  it  like  a  sieve.  After  puddling  and 
tamping  the  bottom  by  the  use  of  stock,  however,  no  difficulty 
was  experienced  in  making  it  water  tight. 

The  first  requisite  for  an  earth  reservoir,  if  unlined,  is  an 
impervious  stratum  within  easy  reach  of  the  ground.  If  this 
stratum  consists  of  clay,  or  clay  and  sand,  the  usual  method  of 
construction  is  to  dig  a  trench  down  to  the  stratum  and  fill  it 
with  water-tight  material  put  in  in  layers,  rammed  or  rolled 
in  place.  The  bank  as  it  is  built  up  is  compacted  in  some 
manner,  either  by  tamping  or  by  rollers,  and  the  interior  at 
least,  of  the  embankment,  is  made  of  water-tight  material. 

Puddle,  which  consists  of  a  mixture  of  clay,  sand,  and  gravel, 
is  often  used  for  this  purpose.  Sometimes  equal  proportions 
of  the  three  materials  are  used.  They  are  carefully  mixed  and 
moistened  and  compacted.  Puddle  is  usually  used  in  the 
trench  below  the  ground,  and  also  in  the  core  of  the  reservoir 
bank.  The  following  puddle  mixture,  laid  in  2-inch  layers, 
harrowed  and  rolled,  is  sometimes  employed:* 

Coarse  gravel 0  .74  cubic  yard 

Fine  gravel 0 .26     "       " 

Sand 0.11     "       " 

Clay 0.15     "       " 

1.26     "       " 

making  one  cubic  yard  of  puddle. 

Embankments  are  usually  constructed  of  material  which  is 
close  at  hand,  as  the  distance  which  the  dirt  must  be  handled 
is  a  very  important  item  in  the  cost  of  construction.  Where 
it  has  been  impossible  to  obtain  clay,  loam  has  successfully  been 
used  as  a  substitute  in  puddle. 

With  regard  to  the  cost  of  earthwork,  the  following  figures  are 
taken  from  H.  P.  Gillette's  "  Earthwork  and  Its  Cost,"  and  are 
based  on  15  cents  per  hour  for  labor,  and  10  cents  per  hour  per 

*  Fanning. 


76 


PRACTICAL  IRRIGATION. 


horse.  They  do  not  include  charges  for  foreman,  timekeeper, 
blacksmith,  watchman,  water-boy,  interest,  and  rental  of  plant, 
nor  cost  of  grubbing,  draining,  spreading,  rolling,  sprinkling 
and  insurance. 

TABLE  XX. 
COST   OF  EARTHWORK. 


Cost  per  cubic  yard  material, 
cents 

Additional 
for  each 
100  feet 

Length  of  haul  —  feet 

50 

18.7 
18.4 
9.0 
7.5 
9.2 

9.5 
10.5 

17.0 

100 

18.7 
18.4 
10.0 
8.75 
9.2 

9.5 
10.5 

17.0 

200 

19.4 
18.8 
14.0 
11  .5 
11.4 

10.7 
10.5 

17.0 

1000 

25.0 
22.0 
46.0 
33.5 
29.0 

20.3 
13.0 

17.0 

0.7 
0.4 
4.0 
2.75 
2.2 

1  .2 
0.5 

0.1 

Wagons  on  soft  earth  roads   .... 
Wagons  on  hard  roads    

Drag  scrapers        

Wheel  scrapers  No   1       

Wheel  scrapers  No   2           

Wheel  scrapers  No.  3,  with  snatch 
team  

Elevating  grader  on  soft  earth  roads 
Cars  loaded  by  hand  and  hauled  by 
team 

These  costs  are  for  average  earth,  readily  plowed.  The  cost 
of  rolling  with  a  2-ton  grooved  roller  will  be  one-half  cent  per 
cubic  yard,  and  on  large  work,  by  the  use  of  a  Shuart  grader, 
the  cost  of  spreading  will  be  the  same.  With  proper  appliances, 
sprinkling  can  be  done  for  0.4  cent  per  cubic  yard,  if  water  is 
near  at  hand.  Harrowing  will  cost  0.35  cent  per  cubic  yard. 

Earth  has  been  handled  hydraulically  in  making  fills,  at  a 
cost  of  4  to  16  cents  per  cubic  yard.  The  water  pressure  for 
hydraulicking  earth  is  usually  obtained  by  gravity,  but  occasion- 
ally it  has  been  obtained  by  pumping. 

The  cost  of  reservoir  embankments  will  usually  lie  between 
10  cents  and  30  cents  per  cubic  yard.  In  Southern  Texas  wages 
are  low,  the  average  pay  of  Mexican  labor  per  day  being  between 
50  cents  and  38  cents,  without  board.  This  labor,  it  is  true, 
is  not  as  efficient  as  American  labor  further  north,  but  neverthe- 
less it  is  far  cheaper  considering  the  work  done.  Unless  condi- 
tions are  unfavorable,  a  cost  of  10  cents  per  cubic  yard  will 
usually  insure  the  contractor  a  good  profit  for  the  construction 
of  embankments  with  short  hauls.  In  the  North  20  to  25  cents 
per  cubic  yard  might  be  a  fair  price  to  expect  for  such  work. 


METHODS   FOR    OBTAINING    WATER. 


17 


The  banks  of  reservoirs  of  any  extent  must  be  protected  from 
the  waves  in  some  manner.  Riprap,  consisting  of  stone  roughly 
lnii  1  in  place,  is  commonly  used  for  such  purposes,  the  thickness 
of  the  layer  usually  being  10  to  12  inches.  Assuming  that 
riprap  weighs  100  pounds  per  cubic  foot  to  allow  for  the  voids, 
the  weight  of  one  cubic  yard  will  be  2700  pounds,  and  the 
weight  of  one  square  yard  10  inches  thick,  750  pounds.  At  35 
cents  per  hour  for  team  and  driver,  it  will  cost  to  haul  the  riprap, 
from  5  to  10  cents  per  mile,  per  square  yard,  depending  on  the 
roads.  Assuming  7  cents,  it  will  cost  21  cents  for  a  three-mile 
haul.  To  this  must  be  added  the  cost  of  loading  and  unload- 
ing, and  distributing  the  stone,  say,  9  cents  per  square  yard, 
or  30  cents  total,  provided  the  stone  is  readily  obtainable  without 
blasting.  Much  of  the  Mississippi  levee  work  has  been  rip- 
rapped  10  inches  thick,  at  a  cost  of  27  cents  per  square  yard, 
the  stone  being  conveyed  about  40  miles  by  barges. 

The  proper  slope  for  earth  banks  varies  with  the  material  of 
the  banks,  and  the  protection  of  the  same  from  waves.  In 
general  the  inside  slopes  of  earth  reservoirs  are  from  3  to  1,  to 
2  to  1,  and  the  outside  slopes  from  2  to  1,  to  1J  to  1. 

Table  XXI,  taken  from  Molesworth,  gives  the  angles  of 
repose  of  various  earths. 

TABLE  XXI. 
ANGLES  OF  REPOSE. 


Degrees 

Horizontal 

Vertical 

Compact  earth  
Clay,  well  drained 

50 
45 

.75 
1  00 

1 
1 

Gravel  

40 

1  25 

1 

Dry  sand  
Wet  sand  
Vegetable  earth  (loam)  
Wet  clay 

38 
22 
28 
16 

1.25 
2.50 
1  .75 
3  00 

1 
1 

1 
1 

Gravel  shores  exposed  to  wave  action  will  finally  take  a  slope 
of .")  to  1,  to  10  to  1.  If  the  bank  is  protected  by  riprap,  it  may 
be  given  a  steeper  slope  than  if  unprotected.  Riprap  does  not 
need  to  be  carried  to  the  base  of  a  reservoir  bank,  as  the  action 
of  the  waves  from  shallow  water  has  comparatively  little  effect, 


78  PRACTICAL  IRRIGATION. 

and  as  further  little  damage  will  be  done  should  slight  caving 
ensue  near  the  base  of  a  bank,  provided  there  is  plenty  of 
material  above  to  fall  in  place. 

When  embankments  are  constructed  from  40  to  50  feet  in 
depth,  it  is  customary  to  use  a  berm  on  the  inside.  The  berm 
is  a  horizontal  offset  in  the  slope  of  the  bank,  and  is  particu- 
larly designed  to  allow  for  settlement  or  caving  of  the  embank- 
ment. 

Reservoir  Linings.  —  Where  reservoirs  will  not  retain  water, 
due  to  seepage,  it  is  necessary  to  line  the  bottom  and  sides  with 
impervious  material.  Puddle  is  sometimes  used  for  this  pur- 
pose. The  gravel  is  first  spread  in  a  3-inch  layer  over  the  surface, 
and  then  clay  over  the  gravel,  and  sand  over  the  clay,  in  proper 
proportions.  According  to  Gillette,  the  cost  of  such  puddle 
lining  is  as  follows : 

Spreading  by  hand 8  cents  per  cubic  yard 

Harrowing      5       "     "         "         " 

Sprinkling 2       "     "         "         " 

Rolling        5       "     " 

20       "     " 

To  this  must  be  added  the  cost  of  hauling  the  various  materials. 
If  this  cost  be  40  cents,  corresponding  to  a  mean  haul  of  1  mile 
by  wagons  on  good  roads,  puddle  would  cost  60  cents  per  cubic 
yard,  or  10  cents  per  square  yard,  6  inches  thick. 

Concrete  is  sometimes  used  for  reservoir  lining.  The  cost 
varies  widely,  depending  on  the  length  of  hauls  and  on  the 
strength  of  the  mixture.  The  materials  for  concrete  will  usually 
cost  from  $3  to  $8  per  cubic  yard.  The  cost  of  mixing  and 
spreading  will  depend  largely  on  the  size  of  the  undertaking. 
A  large  reservoir  near  New  York  was  lined  at  a  cost  of  60  cents 
per  cubic  yard  for  mixing,  distribution  and  spreading,  6  inches 
thick.  If  the  concrete  cost  $5.40  for  materials,  it  would  then 
cost  $1.00  per  square  yard,  6  inches  thick. 

Small  earth  tanks  have  been  lined  with  the  following  mixture : 
73  per  cent  of  sand  is  mixed  with  2  per  cent  of  air-slacked  lime, 
and  then  poured  into  25  per  cent  of  coal  tar.  The  mixture  is 
applied  53  pounds  per  square  yard  of  surface,  or  about  0.5  inch 
thick.  The  surface  is  then  coated  with  tar  paint,  which  has 
first  been  heated  and  flashed  until  the  grease  is  burned  out. 


METHODS    FOR    OBTAINING    WATER. 


79 


MATERIAL  PER  SQUARE  YARD. 

Lime 0 .7  pound. 

Sand 38  .3  pounds  equal  0.011  cubic  yard. 

Tar   14  .0  pounds. 

This  would  be  too  thin  a  coating  to  apply  to  a  reservoir  of  any 
capacity,  however,  without  a  good  foundation  of  rock  or  stone. 


Wells. 

The  usual  means  of  tapping  the  underground  water-supply  is 
by  sinking  a  well.  In  the  following  chapter  the  nature  of  wells 
is  treated  at  length.  In  case  the  sides  of  the  well  are  sufficiently 
firm  not  to  cave,  the  well  need  not  be  curbed  or  cased,  but  if,  as 
is  usually  the  case,  the  material  of  the  sides  will  not  stand  up, 
it  is  necessary  to  provide  suitable  supporting  material.  The 
majority  of  irrigation  wells  are  bored  wells  and  are  either  open- 
bottom  wells  or  have  their  casing  provided  with  a  strainer.  If 
the  stratum  above  the  water-bearing  stratum  is  of  such  a  nature 
that  it  will  be  sufficiently  self-supporting,  the  open -bottom  well 
is  preferable,  since  it  causes  less  restriction  to  flow  into  the 


Fig.  17.     Proper  Casing. 


Fig.  18.    Casing  too  Deep. 


casing.  In  some  places,  however,  the  nature  of  the  material 
of  this  stratum  is  such  that  it  will  ultimately  cave,  and,  in  this 
event,  it  is  necessary  to  insert  a  strainer  in  the  well.  If  an 
open-bottom  well  be  used,  great  care  should  be  taken  to  stop  the 
casing  just  at  the  top  of  the  water  stratum,  and  not  to  let  it 
project  into  it,  with  the  inevitable  result  that  it  will  throw  out 
large  quantities  of  sand,  greatly  increasing  the  possibilities  of 
caving.  This  is  evident  by  reference  to  Figs.  17  and  18,  the 
former  representing  the  casing  properly  put  down  and  the  latter 


80  PRACTICAL  IRRIGATION. 

showing  the  effect  of  a  casing  too  far  down.     Where  a  strainer 
must  be  employed,  it  should  fulfill  the  following  qualifications: 

1.  It  should  be  sufficiently  strong  and  of  such  material  as 
not  to  be  injured  when  being  put  down  the  well  or  by  chemical 
action  of  the  well  water. 

2.  The  openings  should  be  sufficiently  large  to  admit  water 
and  keep  out  sand,  or  at  least  to  prevent  the  coarser  sand  which 
will  collect  around  the  strainer  from  passing  through. 

3.  The  openings  should  increase  in  size  toward  the  inside, 
to  ensure  that  particles  of  dirt  which  start  through  the  openings 
will  be  carried  through  and  will  not  plug  up  the  holes. 

4.  The  resistance  to   flow   of  water    should  be  as  small  as 
possible.     The  strainer  should  hence  be  as  large  in  diameter, 
and  as  long  as  possible.    The  resistance  to  the  flow  of  well 
water  limits  the  output  of  the  well.     This  resistance  is  composed 
of  friction  in  the  pipe,  in  the  entrance  to  the  casing,  and  in  the 
ground  leading  to  the  casing.     Pipe  friction  is  dependent  on 
the  size   and  depth  of  well.     Friction  at  entrance  depends  on 
the  strainer,  its  length  and  diameter,  as  well  as  the  nature  of 
the  ground  immediately  surrounding  the  same.     Friction  in  the 
ground  depends  on  the  quality  and  thickness  of  the  water 
stratum.    The  coarser  the  sand  and  gravel,  the  less  is  the  resist- 
ance to  flow,  and  the  better  the  indications  for  a  good  well,  other 
things  remaining  the  same.    The  existence  of  a  spring  is  evi- 
dence of  the  fact  that  water  in  the  ground  is  under  pressure,  and 
is  a  good  indication  of  the  probability  of  obtaining  an  artesian 
well,  if  the  elevation  of  the  well  is  not  far  above  that  of  the 
spring.    Although  in  the  majority  of  cases  the  probable  results 
of  a  well  may  be  inferred  from  wells  near  by,  still  it  should 
always  be  borne  in  mind  that  it  is  practically  impossible  to  be 
certain  of  the  result  of  sinking  a  well,  owing  to  the  formation 
of  the  ground  and  faults  therein,  and  that  it  is  not  infrequently 
the  experience  that  of  two  wells  of  the  same  size  and  depth 
but  a  very  short  distance  apart,  one  will  have  an  abundance  of 
water  while  the  other  may  have  practically  no  supply. 

In  a  certain  case  where  water  was  in  limestone  formation  and 
many  excellent  flowing  wells  were  bored,  striking  a  subterranean 
channel,  one  well  in  the  same  district  had  a  very  weak  artesian 
flow,  though  it  was  much  deeper  than  surrounding  wells.  The 
water-bearing  formation  was  of  a  close -grain  rock  which  strongly 


METHODS    FOR   OBTAINING    WATER.  81 

throttled  the  supply,  and  the  owner  was  convinced  that  the  only 
reason  his  well  gave  so  little  water  was  simply  because  he  was 
a  poor  man. 
Among  the  strainers  employed  may  be  mentioned  the  following: 

1.  The  well  casing  is  perforated  from   within 
by  a  punch  which  cuts  a  slot  bulging  outwards 
about  sV  inch  wide  and  1  inch  long.    This  forms 
an  excellent  strainer  for  some  soils.    The  per- 
forations, which  are  numerous,  are  usually  made 
before  the  screen  is  put  down.     (See  Fig.  19.) 
Sometimes  the  perforations  are  made  by  a  per- 
forator or  cutter  working  within  the  casing  after 

it  is  in  place,  but  this  is  less  liable  to  give  good    -^  \9'  Casing 
results,  and  the  holes  are  liable  to  be  too  large. 

2.  The  well  casing  is  drilled  with  numerous  small  holes,  and 
the  outside  of  the  casing  is  wound  with  copper  wire  leaving 
slight  spaces  between  the  convolutions.    The  wires  are  then 
soldered  longitudinally  to  hold  them  in  place. 

3.  A  similar  strainer  is  used,  covered  on  the  outside  by  copper 
or  brass  gauze. 

4.  A  strainer  similar  to   (2)  is  used,  except  that  the  wire  is 
of  a  trapezoidal  shape,  with  the  shorter  leg  inside  next  to  the 
pipe  and  the  longer  leg  outside,  so  that  there  is  a  taper  passage, 
and  particles  starting  to  enter  the  casing  will  probably  continue 
through. 

5.  The  Cook  strainer  consists  of  a  brass  pipe  perforated  from 
the  inside  by  fine  circumferential  slots.     In  case  this  strainer 
encounters  resistance  in  putting  it  down,  it  is  liable  to  close 
some  of  the  slots. 

6.  Some  so-called  strainers  are  used,  in  which  the   pipe  is 
simply  bored  with  holes  about  f  inch    in   diameter.    This  in 
reality  is  not  a  strainer,  and  has  about  the  same  effect  as  an 
open-bottom  well,  except  that  the  water  is  more  throttled  by 
entrance  to  the  small  holes,  and  should  caving  of  the  upper 
strata  occur  the  well  is  not  so  likely  to  be  entirely  stopped  up. 

In  well  boring  it  is  quite  common,  especially  in  deep  wells, 
to  encounter  several  water-bearing  strata,  and  frequently 
the  quality  of  the  water  obtained  therefrom  is  such  as  to 
be  absolutely  unfit  for  irrigation,  due  to  impregnation  with 
the  salts  in  the  ground.  Such  strata  must  be  cut  off  and 


82  PRACTICAL  IRRIGATION. 

prevented  from  mingling  with  good  water,  in  case  the  same 
be  found. 

In  some  wells  the  water  pressure  is  sufficient  to  raise  the 
water  above  the  ground  level  and  cause  artesian  flow,  but  in  the 
great  majority  of  cases  the  water  stands  below  the  ground  and 
must  be  elevated  before  it  can  be  used.  Drawing  on  the  well 
will  cause  the  water  to  sink  further  in  the  well,  necessitating  an 
additional  lift.  The  effect  of  the  discharge  on  the  level  of  water 
in  the  well  has  an  important  effect  on  the  cost  of  raising  water 
and  will  be  discussed  more  fully  in  the  next  chapter. 

If  the  discharge  of  the  well  deriving  its  water  from  sand 
strata  be  too  great,  it  will  tend  to  carry  the  sand  into  the  well, 
resulting  in  sanding  up  of  the  well.  In  one  case  a  certain 
artesian  well  was  cleaned  out  in  the  following  manner:  A 
small  pipe  was  run  100  feet  down  the  well,  and  was  connected 
at  the  top  to  a  receiver  in  which  a  high  air  pressure  had  been 
pumped  up.  When  the  air  valve  was  opened  the  discharge 
shot  the  water  out  of  the  well  like  a  geyser.  When  the  water 
subsided,  the  level  fell  and  remained  several  feet  down  the  well. 
A  sounding  showed  that  the  bottom  of  the  well  had  filled  up 
with  about  40  feet  of  sand,  shutting  off  the  flow.  The  air  com- 
pressor was  then  started  pumping  gradually  from  the  well,  and 
in  a  few  minutes  run  had  removed  not  only  the  sand  blown  into 
the  well  but  additional  sand  which  was  in  the  bottom,  and 
restored  the  full  artesian  flow. 

Where  the  water  stands  below  the  level  of  the  land  to  be 
irrigated,  it  must  first  be  elevated  before  it  can  be  used  for  irri- 
gation. For  this  purpose  some  form  of  pumping  machinery 
must  be  used.  The  use  of  machinery  for  the  elevation  of  water 
dates  back  to  the  earliest  records  of  history,  some  of  the  first 
forms  consisting  of  a  bucket  on  a  long  lever,  the  center  of  which 
was  pivoted  on  a  cross  bar.  This  device  was  operated  by  hand 
by  a  man  on  the  other  end  of  the  lever.  Even  to-day,  places 
can  be  found  where,  when  a  dry  spell  comes  on,  the  farmers 
will  make  frantic  efforts  to  save  their  crops  by  hauling  water  in 
barrels  and  distributing  it  by  hand.  Of  course,  such  crude 
irrigation  is  very  expensive,  and  usually  quite  inefficient,  due 
to  the  small  supply  of  water  used. 

In  addition  to  the  pump,  some  form  of  motor  or  engine  must 
usually  be  used  to  drive  the  pump.  The  motive  power  may  be 


METHODS   FOR    OBTAINING  WATER.  83 

either   steam,    hydraulic,    electric,  pneumatic,  or  else   gas   or 
gasoline,  and  sometimes  draft  animals  are  used. 

While  gravity  systems  are  usually  preferable,  still,  in  many 
cases,  where  the  development  cost  is  high,  the  cost  of  water  so 
obtained  will  exceed  the  cost  of  pumped  water,  especially  where 
the  lift  is  low.  In  obtaining  water  by  pumping,  four  things 
must  be  considered: 

1.  The  vertical    height  which    the    water  must  be  raised  to 
elevate  it  sufficiently  to  reach  the  highest  point  on  the  land. 

2.  Variations  due  to  the  season,  or  other  causes,  in  the  water 
level. 

3.  The  amount  the  water  level  will  be  affected  by  pumping, 
and 

4.  Whether  the  available  supply  is  sufficient  at  all  times  to 
furnish  the  pump  with  the  required  supply. 

It  is  impossible  to  raise  water  by  suction,  a  distance  greater 
than  34  feet  at  sea  level  and  less  distance  at  higher  altitudes. 
In  practice,  from  28  to  30  feet  will  be  about  the  limit  at  sea  level. 
Consequently  the  pump  must  be  located  a  distance  less  than  30 
feet  above  the  lowest  level  to  which  the  surface  of  the  water 
supply  for  the  pump  will  fall.  Also,  generally,  it  is  desirable  for 
most  forms  of  pumps  not  to  be  submerged  when  the  water  is  at 
its  highest  level. 

Usually  the  ground  water  and  also  the  standing  water  level 
in  wells  is  subject  to  annual  variations  of  several  feet,  depending 
on  the  seasons  and  on  the  water  supply  for  the  strata  on  which 
the  well  draws.  It  is  customary  in  many  places  in  pumping 
from  wells  to  dig  pits  in  which  to  set  the  pumps  in  order  to 
locate  them  sufficiently  near  the  water  level  to  be  within  the 
suction  limit.  It  is  generally  preferable,  if  possible,  to  locate 
the  pump  so  that  it  will  not  have  to  operate  under  too  high  a 
vacuum,  since  suction  piping  is  more  difficult  to  keep  tight  than 
pressure  piping,  and  since,  moreover,  a  very  small  leak  of  air,  or 
the  air  necessarily  entrained  in  the  water  (particularly  in  well 
water),  will  expand  greatly  when  it  enters  the  pump  under  a 
high  vacuum,  and  hence  will  cut  down  the  efficiency  of  the  pump, 
and  may  make  it  loose  its  priming. 

It  is  important  to  provide  good  foundations  and  suitable 
housing  for  pumps  and  pumping  machinery,  to  ensure  long 
life.  The  depreciation  of  much  of  the  machinery  used  in  irri- 


84  PRACTICAL  IRRIGATION. 

gation  pumping  is  usually  very  great,  due  to  neglect  and  improper 
covering.  To  install  a  plant  to  operate  economically  requires 
a  careful  consideration  of  the  type  of  pump  motor  or  engine 
and  fuel  best  suited  to  the  conditions  of  the  case,  as  will  be 
explained  more  fully  in  the  chapter  on  pumping. 


CHAPTER  VIII. 
WELLS. 

Law  of  Flow  of  Wells. 

IN  the  consideration  of  the  installation  of  a  well  pumping 
plant,  it  is  essential  to  have  some  idea  of  the  amount  of  water 
available,  and  of  the  depth  from  which  it  must  be  pumped. 
It  is  a  question  for  the  engineer  to  determine  whether  he  will 
pump  from  two  or  more  wells  either  a  greater  supply,  from  the 
same  depth,  or  else  the  same  supply  with  a  diminished  lift, 
thus  either  having  a  station  of  greater  capacity  or  else  one  of 
the  same  capacity,  but  with  smaller  engines  and  decreased  fuel 
expense.  For  example,  suppose  the  ground  water  stands  12  feet 
from  the  ground,  would  it  pay  better  to  put  in  one  well  deliver- 
ing 2  cu.  ft.  per  sec.  of  water  and  lowering  the  water  20  ft.  in 
the  wells  or  else  to  follow  one  or  other  of  the  two  following 
plans?  Put  in  two  wells  delivering  3.5  cu.  ft.  per  sec.  and 
lowering  the  water  20  ft.  in  wells,  or  else  put  in  two  wells 
delivering  2  cu.  ft.  per  sec.  lowering  the  water  12  ft.  in  the  wells. 
In  the  first  and  second  cases  the  lift  would  be  32  ft.,  and  in  the 
last  case  24  ft.  Hence,  if  2  cu.  ft.  per  sec.  were  all  the  water 
desired,  only  two-thirds  of  the  boiler  and  engine  capacity  would 
be  necessary  in  the  third  case,  together  with  a  greatly  diminished 
fuel  expense,  too,  over  what  the  first  case  would  demand. 

The  wells  will  usually  interfere  somewhat  with  the  flow  from 
each  other  when  near  at  hand.  In  order  to  form  an  intelli- 
gent estimate  on  this  subject,  a  knowledge  of  the  flow  of  water 
into  wells  is  important.  Water  will  rise  to  a  certain  level 
in  a  well  when  not  flowing,  due  to  the  hydrostatic  pressure 
in  the  ground.  If  this  level  be  above  the  ground,  then, 
if  the  well  casing  be  cut  off  at  the  ground,  an  artesian  flow  will 
result.  Should  the  water  stand  below  the  ground  and  the 
well  be  lowered  further  by  pumping,  the  well  will  similarly 

85 


86  PRACTICAL  IRRIGATION. 

flow.*  An  artesian  well  is  not  different  from  a  pumped  well, 
except  that  in  the  former  the  static  water  level  is  above  the 
point  of  discharge,  the  law  of  flow  in  either  case  being  identical. 
In  a  given  well  the  flow  is  dependent  solely  on  the  distance  the 
hydrostatic  head  is  lowered  by  artificial  or  natural  means,  and 
it  is  this  lowering  of  head  which  is  effective  in  causing  flow. 
The  relation  between  the  flow  and  the  lowering  of  the  head  of 
the  well  from  the  level  of  standing  water  in  the  same  is  known 
as  the  law  of  flow  of  the  well.  This  head,  which  is  effective  in 
causing  flow,  is  used  up  in  friction  in  the  ground,  in  entrance  to 
the  casing,  and  in  friction  in  the  casing  of  the  well.  However, 
the  laws  governing  the  flow  of  water  into  wells  are  not  always 
clearly  exemplified,  and  the  results  of  tests  to  determine  the 
same  are  liable  to  be  somewhat  confusing,  owing  to  a  variety 
of  causes.  The  general  law  governing  the  flow  of  a  fluid  through 
a  porous  or  finely  divided  medium,  such  as  sand,  is  that  the  flow 
is  directly  proportional  to  the  pressure  causing  the  flow.  In 
other  words,  if  Q  =  cu.  ft.  per  sec.  be  delivered  from  a  unit 
cross-section  and  H  =  head  necessary  to  force  Q  through  a 
unit  length,  then  H  =  KQ,  where  K  is  a  constant. 

The  flow  of  fluid  in  a  pipe  is  subject  to  the  law  that  the 
quantity,  Q,  delivered  per  unit  time  from  a  fixed  length  of  a 
given  size  pipe,  varies  as  the  square  root  of  the  head,  A,  causing 
said  flow.  In  other  words,  h  =  kQ2  where  A;  is  a  constant. 

Hence  if  Q  be  the  flow  of  a  well,  the  distance  the  water  level 
must  be  lowered  in  the  well  to  produce  this  flow  is  H1  =  H  + 
h  =  KQ  +  kQ2,  H  being  the  head  necessary  to  force  water 
through  the  ground  and  into  the  well,  and  h  the  head  used  up 
in  overcoming  the  friction  in  the  pipe  in  the  well.  Where  the 
main  loss  consists  in  flow  through  sand  or  porous  media  the 
equation  is  practically  of  the  first  degree. 

Among  the  causes  which  may  obscure  the  action  of  these  two 
laws  may  be  mentioned  the  following: 

1.  Change  in  the  nature  of  the  porous  medium. 

(a).  It  is  not  uncommon  for  wells  to  be  developed  by 
pumping  or  flowing.  This  is  largely  caused  by  a  rearrange- 

An  artesian  well  is  often  defined  as  a  well  wherein  the  water  from  a  given 
stratum  will  rise  above  the  top  of  the  stratum.  In  the  usual  acceptance 
of  the  term,  however,  the  water  must  be  under  sufficient  pressure  to  deliver 
a  flow  at  the  ground  level. 


WELLS. 


87 


ment  of    the  strata  through  which  the  water  passes,  making  a 
decreased  resistance  to  flow. 

(6).  Sanding  up  of  the  well.  Wells  are  liable,  to  be  filled 
with  sand  to  such  an  extent  that  the  standing  water  level  will 
be  lowered  many  feet. 

(c).  Plugging  up  of  strainers,  or  of  perforations  in  the  casing. 

2.  Leakage  of  water. 

If  two  water  strata  of  different  static  levels  are  united  in  a 
well,  there  will  be  a  flow  of  water  from  the  stratum  of  higher  to 
that  of  lower  pressure. 

If,  however,  the  water  is  lowered  by  any  cause  below  the  lower 
static  pressure,  outflow  will  be  obtained  from  each  stratum. 

Leakage  of  water  also  occurs  where  the  well  casing  is 
improperly  put  down,  and  the  water  follows  up  the  outside  of 


7777;  ~ 


c  water  level 


Fig.  20.    Water  at  A  and  B.        Fig.  21.     Water  between  A  and  B. 

the  casing  into  other  strata.  This  is  liable  to  be  a  cause  of 
serious  loss  in  artesian  wells.  Holes  in  the  casing  may  also 
cause  leakage  between  different  water  strata. 

3.  The  effect    of  neighboring  wells,  which  affect  the  ground 
water  level. 

4.  The  time  element. 

In  making  tests  of  variation  of  flow  and  head,  sufficient  time 
must  be  allowed  for  the  quantities  to  settle  down  to  fairly 
constant  values. 

5.  The  effect  of  wet  and  dry  years,  which  may  affect  largely 
the  static  water  pressures. 


88 


PRACTICAL  IRRIGATION. 


6.  When  water  is  lowered  beyond  the  level  of  a  stratum,  in 
such  a  way  that  no  vacuum  is  produced  on  said  stratum,  the 
flow  from  it  will,  of  course,  be  constant. 

This  will  somewhat  complicate  the  relation  between  H  and  Q, 


JO 


i- 


n  I  £  3  V 

flow,  cu.ff.  per  sec. 

Fig.  22.     Case  1. 

and  will  introduce  a  constant  into  the  equation.  Take,  for 
example,  the  case  of  a  well  having  two  water  strata,  A  and  B, 
each  of  which  has  the  same  static  level.  Lower  the  well,  d, 
Fig.  20.  So  long  as  d  is  less  than  /,  then,  calling  Qa  the  flow 
from  A,  and  Q6the  flow  from  B,  Qa  =  dKa,  Qb  =  dKb. 


c«,nfV  *£ 


Fig.  23.     Case  £. 


Fig.  24.     Case 


Hence, 


=        =  -and  Q=  d  (Ara  +  Ar6)  =  d  K, 


Xa    and    Kb    being   the  constants  for  the  strata,  A    and 
respectively. 

When  the  water  level  lies  between  A  and  B  (Fig.  21) 

Qa  =  (c  +  /)  X0 


Q    =  (c  +  /)  Ka  + 


U'KLLS. 


89 


Practically,  we  would  not  get  quite  this  quantity  of  water, 
since  the  upper  part  of  stratum  A  would  not  be  lowered  /  feet, 
immediately  next  to  the  well.  The  actual  value  would  be 
indeterminate,  however,  depending  on  location  of  the  main 
resistance  to  flow  in  stratum  A.  In  the  above,  there  is  supposed 
to  be  no  vacuum  in  the  well  itself,  and  no  appreciable  friction 
loss  in  the  casing. 

Tables  XXII,  XXIII  and  XXIV,  and  curves  in  Figs.  22,  23 
and  24  show  the  relation  between  H  and  Q  in  two  pumped 
stations,  where  a  test  was  made  to  determine  the  same,  and  in 
an  artesian  well. 

TABLE  XXII.  — WELL  TESTS. 
Case  1. 


Well  l. 

Well  2. 

Well  3. 

Well  4. 

Average. 

C-t 
Cu.  ft. 
per  sec. 

H* 

Feet. 

<?• 
Cu.  ft. 
per  sec. 

H. 

Feet. 

Q- 

Cu.ft. 
per  sec. 

H. 

Feet. 

Q- 

Cu.  ft. 

per  sec. 

H. 

Feet. 

Q- 

Cu.  ft. 
per  sec. 

H. 

Feet. 

4.21 
3.98 
3.20 
2.29 
.95 

27.6 
25.2 
22.3 
15.4 
9.0 

4.21 

3.98 
3.20 
2.29 
.95 

27.5 
25.3 
22.2 
15.4 
9.0 

4.21 
3.98 
3.31 
2.20 

.88 

27.2 
25.3 
23.0 
15.3 
9.0 

4.21 
3.87 
3.20 
2.20 

.88 

27.4 
25.2 
21.7 
15.3 
9.0 

4.21 
3.96 
3.23 
2.25 
.92 
.0 

27.4 
25.2 
22.3 
15.3 
8.5 
3.3 

*  H  =  distance  in  feet  from  center  of  horizontal  suction  pipe  to  ground 
water. 

t  Q  =  rate  of  flow  from  all  four  wells. 


TABLE   XXIII.— WELL  TESTS. 

Case  2. 


TABLE   XXIV.— WELL  TESTS. 
Cose  3. 


Q- 

Gal.  per  min. 

H.* 

Feet. 

0 

0 

8.0 

4.5 

9.8 

5.6 

14.3 

7.5 

19.0 

10.0 

22.8 

11  .2 

Q- 
Cu.  ft.  per  sec. 

//.t 
Feet. 

0 

0 

.86 

4.9 

1  .40 

6.5 

1.95 

10.2 

2.12 

12.4 

2.44 

15.9 

*  II  =  distance  in  feet  water  in  well  is  lowered. 

t  //  =  distance  in  feet  well  water  is  lowered  below  point  of  zero  discharge. 


90  PRACTICAL  IRRIGATION. 

In  Case  3  the  well  water  was  throttled,  and  H  obtained  by 
calculation  from  pressure  behind  the  throttle. 

In  Case  1  there  were  four  13-inch  shallow  wells  which  supplied 
water  for  the  pump,  and  consequently  there  was  practically  no 
friction  loss  in  the  casing,  the  whole  loss  being  confined  to  the 
sand,  which  was  the  water-bearing  stratum,  and  to  entrance  to 
the  casing  through  the  perforations. 

In  the  second  case  a  deep-well  pump  was  used  on  a  6-inch  well 
which  was  open  bottomed.  The  rate  of  water  supply  was  so 
small  that  there  was  practically  no  friction  loss  in  the  casing. 

The  two  curves  of  H  and  Q  are  practically  straight  lines,  and 
may  be  represented  by  the  equation,  H  =  KQ,  thus  confirming 
the  results  obtained  in  theoretical  and  experimental  formulae  for 
the  flow  of  water  through  sand. 

The  figures  and  curves  in  Case  3  show  the  relation  between 
H  and  Q  in  an  artesian  well.  The  water-bearing  stratum  was 
rock,  and  the  water  was  found  in  subterranean  passages  and 
chambers  in  the  rock.  The  friction  loss  in  the  well  and  casing 
constituted  the  main  loss  of  head,  and  the  curve  can  be  approxi- 
mately represented  by  the  equation,  H  =  KQ2. 

The  time  element  entered  largely  into  this  test,  and,  as  the 
time  of  making  the  same  was  limited,  this  of  necessity  intro- 
duced some  error  in  the  results. 

The  two  laws  of  the  flow  of  water  are  well  exemplified  by  the 
difference  between  curves  1  and  2  and  curve  3. 

Where  the  friction  is  in  the  pipe,  it  can  be  figured  closely, 
but  where  it  is  in  a  roughly  drilled  uncased  hole,  it  can  be  figured 
only  approximately. 

The  general  law  governing  the  output  of  artesian  water  or 
pump  water  is  H  =  a  +  bQ  +  cQ2;  where  Q  =  rate  of  discharge 
of  well,  a  =  distance  of  static  level  of  the  water  below  the  level 
of  discharge.  (In  an  artesian  well  a  will  be  negative,  as  the 
water  will  stand  without  flow  above  the  level  of  the  discharge.) 
H  =  vertical  distance  between  the  level  to  which  water  is 
lowered  in  the  well  and  the  point  of  discharge.  6  and  c  are 
constants.  In  the  case  of  the  artesian  well  not  pumped,  H 
would  be  zero,  and  the  equation  would  then  be  —  a  =  bQ  +  cQ2. 
As  a  general  proposition  it  can  be  said  that  the  head  causing 
flow  in  a  well  is  used  up  in  overcoming  the  frictional  and  other 
losses  in  the  ground  strata,  and  at  entrance  to  the  casing,  and 


WELLS.  91 

also  in  friction  in  the  casing  itself.  The  pipe  losses,  and  losses 
of  head  at  entrance,  if  the  well  is  open  bottomed,  may  be  cal- 
culated from  the  tables  of  friction  losses  and  velocity  heads  for 
the  flow  of  water  in  the  pipes.  As  an  approximation,  suffi- 
ciently accurate  for  practical  purposes,  it  may  be  assumed  that 
losses  of  this  kind  vary  as  the  square  of  the  velocity,  and  hence 
as  the  square  of  the  flow  of  the  well.  Hence  the  value  of  c 
may  be  calculated,  and  the  losses  in  the  ground  and  flow  into 
the  casing  may  be  assumed  to  vary  according  to  the  first  power 
of  the  flow,  and  hence  will  contribute  solely  to  the  coefficient,  b. 
There  is  no  practical  means  of  ascertaining  this  coefficient, 
except  from  an  actual  test,  which  must  hence  be  made  in  order 
to  be  assured  of  the  correctness  of  the  figures.  As  an  approxi- 
mation, however,  it  can  be  determined  by  calculation  from  the 
measured  flow  of  the  well  and  the  height  to  which  the  water 
would  rise  above  the  outlet  without  flow. 

In  a  pumped  well,  the  pump  must  operate  against  a  head,  a, 
to  start  to  deliver  water.  H  will  represent  the  head  against 
which  the  pump  must  operate  to  supply  the  increased  delivery. 

To  illustrate  the  method  of  calculation  employed,  assume  that 
an  artesian  wrell  is  of  the  open-bottom  type  and  is  composed  of 
200  feet  of  4-inch  pipe  and  500  feet  of  6-inch  pipe  and  is  deliver- 
ing a  flow  of  352  gal.  per  min.  The  losses  in  head  are  as  follows: 

*  Loss  of  head  at  entrance  to  4-inch  casing  =  i  velocity  head  =    0.63  feet 

*  Friction  in  200  feet  4-inch  pipe  =  15.3    feet 
Friction  in  500  feet  6-inch  pipe  =    5.7    feet 
Loss  of  head  where  pipe  changes  =  Head  due  to  difference  of 

velocities  in  pipes: 

Velocity  in  4-inch  pipe  =  9  feet  per  second 
Velocity  in  6-inch  pipe  =  4  feet  per  second 

Hence  lost  head= velocity  head  due  to  5  feet  per  second  =    0.39  feet 
Velocity  head  in  6-inch  pipe  =    0.25  feet 

Hence  total  loss  of  head  due  to  pipe  losses  =  22.3    feet 

If  the  measured  head  in  the  pipe,  to  which  the  water  would 
rise  above  the  point  of  discharge,  be  40  feet,  then  the  loss  in 
the  ground  strata  would  be  40  —  22.3  =  17.7  feet,  which  would 
be  the  head  required  to  force  a  flow  of  352  gal.  per  min.  into 
the  well.  Assuming  that  the  resistance  to  flow  in  the  ground 
strata  and  into  the  well  varies  directly  as  the  flow,  the  fol- 

*  See  page  108. 


92  PRACTICAL  IRRIGATION. 

lowing  values  can  be  substituted  in  the  equation  of  the  flow 
of  the  well  when  discharging  without  pump: 

H  =  0 
a  =     -40 
cQ2  =  c  X  3522  -  22.3. 


Hence,  c  -  .00018 

17.7 


.050- 


Hence,  the  equation  becomes  H  +  40  =  .00018 Q2  +  .05 Q. 

If  it  were  desired  to  double  the  flow  from  the  well,  then  by 
substituting  the  necessary  value  for  Q  in  this  equation,  the 
corresponding  value  of  H  would  be  84  feet.  In  other  words, 
in  order  to  double  the  output  of  the  well  it  would  be  necessary 
to  lift  the  water  by  the  pump  against  a  head  of  84  feet. 

Suppose,  now,  that  with  the  same  length  and  conditions  of 
casing,  the  static  head  of  the  well  is  8  feet  above  the  level  of 
discharge,  then  a  =  —  8.  Suppose,  also,  that  when  the  well 
is  discharging  freely,  due  to  artesian  flow,  the  rate  of  discharge 
is  88  gal.  per  min. ;  by  similar  computations  it  can  be  shown  that 
c  =  0.00018  and  b  =  0.075.  In  order  to  double  the  rate  of 
flow  of  this  well,  it  can  be  shown  that  the  pump  would  have  to 
operate  against  a  head  of  10.8  feet,  which  is  a  moderate  lift. 
Hence,  were  the  first  cost  of  the  well  high,  it  would  probably 
pay  to  supplement  the  natural  flow  of  the  well  by  the  aid  of  a 
pump,  since  the  output  would  be  doubled  at  a  comparatively 
small  initial  expense,  requiring  about  a  2-horsepower  motor 
and  corresponding  pump.  On  the  other  hand,  in  the  first  case 
considered,  owing  to  excessive  lift  it  would  probably  not  pay  to 
install  a  pump  to  assist  the  well.  These  two  cases  will  illus- 
trate in  a  general  way  the  problem  of  obtaining  additional  water 
from  wells  by  pumping.  If  the  pressure  in  the  well  is  low  and 
is  used  up  mainly  in  overcoming  resistance  to  the  flow  in  the 
ground,  and  not  in  pipe  friction,  then,  in  general,  pumps  can  be 
advantageously  used  to  increase  the  well  flow;  but,  on  the 
other  hand,  if  the  static  head  in  the  well  is  large  and  a  con- 
siderable part  is  used  up  in  overcoming  the  pipe  resistance, 
then  the  additional  water  can  be  obtained  only  at  the  expense 


WELLS.  93 

of  a  considerable  expenditure  of  energy,  since  the  frictional 
losses  vary  as  the  square  of  the  flow.  This  method  of  calcu- 
lation of  the  flow  of  wells  and  variations  in  the  same,  while  not 
strictly  accurate,  owing  to  causes  already  explained,  still  will 
answer  approximately,  provided  more  definite  information  can- 
not be  obtained.  It  is  preferable,  where  tests  can  be  made,  to 
put  in  a  temporary  pump,  to  see  the  actual  performance  of  the 
well.  In  practice  it  may  be  considered  as  the  safest  plan  for 
determining  the  flow  of  the  well. 

Another  method,  however,  which  may  be  adopted  in  artesian 
wells,  is  to  throttle  the  discharged  water  and  note  the  variation 
of  discharge  rate  for  various  pressures  at  the  top  of  the  well. 
By  plotting  these  the  curve  of  well-discharge  rate  and  head  may 
be  obtained,  and  hence  the  law  of  flow  may  be  more  definitely 
determined  for  points  beyond  the  actual  observations. 

There  is.  within  limits,  an  uncertainty  in  calculations  based 
on  the  results  of  observations  of  the  static  head  and  discharge 
rate  at  one  level  only,  which  is  that  in  some  wells  the  lower 
portion  of  the  well  is  not  cased.  The  friction  in  the  well  hole 
would,  in  general,  be  greater  than  friction  in  the  corresponding 
size  of  pipe,  but  the  absolute  value  would  be  somewhat  indeter- 
minate. 

The  level  of  the  water  in  wells  may  fluctuate,  due  to  many 
causes,  which  are  classified  by  A.  C.  Veatch  in  Water  Supply  and 
Irrigation  Paper,  No.  155,  United  States  Geological  Survey,  a 
brief  description  of  which  is  as  follows: 

The  regular  annual  fluctuation  is  due  in  large  part  to  the 
amount  of  rainfall  actually  reaching  the  ground  water.  In  the 
summer  a  large  part  of  the  rainfall  is  evaporated  and  lost  in 
transpiration,  and  does  not  seep  into  the  earth,  but  when  the 
weather  is  cooler  the  reverse  is  true.  The  effect  of  individual 
rains  is  largely  obliterated,  due  to  the  time  element.  Irregular 
distribution  of  rainfall  may  affect  the  curve  of  annual  fluctuation. 
Single  showers  affect  the  water  level  by  transmitting  their 
pressure  to  the  ground  water  through  the  soil  air,  which  cannot 
escape  through  the  wet  surface  of  the  ground.  Fluctuations 
due  to  this  cause  are  abrupt,  while  those  due  to  the  added 
water  from  single  showers  are  gradual, 

A  rise  in  the  barometer  will  cause  the  water  level  to  fall  in 
the  well,  and  vice  versa  for  a  fall  in  the  barometer.  A  rise  of 


94  PRACTICAL  IRRIGATION. 

temperature  will  decrease  the  surface  tension  and  will  release 
the  capillary  water  just  above  the  ground  water  level,  thus 
causing  a  rise  in  the  well  water.  With  a  fall  in  temperature 
the  reverse  result  takes  place. 

Fluctuations  are  produced  by  adjacent  bodies  of  water,  such 
as  rivers,  lakes,  or  the  ocean,  etc.,  either  by  changing  the  height 
of  the  ground  water  discharge,  or  by  seepage  flow  into  the 
ground  water,  or  by  transmitted  pressure,  due  to  plastic  defor- 
mation, which  may  be  felt  even  in  deep  wells.  In  certain 
wells  on  Long  Island  there  was  a  fluctuation  of  5  feet  in  level, 
following  the  tides,  which  fluctuated  8  feet. 

The  settlement  of  the  country,  involving  the  destruction  of 
the  forests,  cultivation  of  fields,  changing  the  nature  of  the 
seepage  surface,  the  irrigation  of  lands,  the  construction  of 
dams,  the  development  of  the  underground  supply  and  the  effect 
of  pumped  or  artesian  wells  all  serve  to  affect  the  level  of  the 
ground  water. 

When  water  flows  into  a  tubular  well,  the  head  in  the  ground 
used  up  in  forcing  the  water  to  the  well  may  be  represented  as 
follows:  Let  2  R  be  the  well  diameter  in  feet,  and  let  2  r  =  diame- 
ter of  a  concentric  circle.  Let  T  =  thickness  in  feet  of  water 
stratum,  and  let  transmission  constant  of  the  sand  be  K.  Let 
Q  =  flow  of  well  —  cu.  ft.  per  min.  Suppose  the  water  level 
in  the  well  is  not  drawn  down  below  the  top  of  the  water- 
bearing stratum,  then,  if  we  consider  the  resistance  to  flow  in 
passing  through  a  cylinder  of  sand  T  high,  of  thickness  dr  and 
radius  r, 


where    H  =  depression  in  feet,  of  water  in  well    due  to   flow, 
and        h  =  depression  at  any  point. 

Hence,  h  =  loge  r  +  A. 


And  integrating  between 

r  =  Rj    and  r  =  r 

77=       0  r  Q  r_ 

=  2  TKn     ge  R  ~  2  TKxloe      gl°  R 


WELLS. 


95 


Table  XXV  gives  values  of  Iog10  —  for  various  casings  and 

diameters  of  surrounding  cylinders.  As  an  approximation, 
the  loss  in  head  in  the  first  10  feet  is  greater  than  the  loss  in  the 
remainder  of  a  100-foot  circle.  However,  these  figures  make  no 
allowance  for  the  loss  of  head  in  entering  the  casing,  which  may 
be  large.  For  example,  if  the  well  is  in  sand,  and  has  a  strainer, 
then,  near  the  casing,  the  water  flow  must  be  diverted  from  its 
path  normal  to  the  cylinder  to  the  openings  in  the  strainer. 
As  the  strainer  area  of  open  spaces  is  necessarily  but  a  small 
percentage  of  the  whole  surface,  the  water  must  necessarily 
move  for  a  small  distance  at  a  velocity  many  times  the  velocity 
in  the  ground,  were  it  to  enter  the  whole  casing.  Also,  if  the 
flow  is  large,  even  if  the  water  stratum  is  of  gravel,  the  head 
lost  in  entrance  to  the  perforations  themselves  may  be  con- 
siderable. 

TABLE   XXV. 
Values  of  log  j  for  Various  Values  of  2R  and  2  r. 


2  R  X  12  = 

Values  of  2  r.     Feet. 

in  inches. 

10. 

100. 

1000. 

10000. 

4 

1.50 

2.50 

3.50 

4.50 

6 

1.30 

2.30 

3.30 

4.30 

8 

1.20 

2.20 

3.20 

4.20 

10 

1  .08 

2.08 

3.08 

4.08 

12 

1  .00 

2.00 

3.00 

4.00 

14 

.93 

1.93 

2.93 

3.93 

Hence  increasing  the  diameter  of  the  wells  will,  in  general, 
result  in  conditions  somewhat  superior  to  what  might  be  expected 
from  the  preceding  table.  If  the  formula  last  given  be  inte- 
grated up  to  r  =  oo  ,  then  the  head  will  also  be  infinite.  Of 
course  the  depression  of  the  ground  water,  occasioned  by  draw- 
ing on  the  well,  decreases  rapidly  when  the  distance  from  the 
well  increases.  To  attempt  to  find  a  general  application  of  the 
formula,  without  further  assumption,  would  be  useless,  as  it 
could  be  considered  to  apply  only  near  the  well,  where  the 
stratum  was  of  the  same  material.  However,  the  general  slope 


96  PRACTICAL  IRRIGATION. 

of  the  ground-water  plane  will  be  a  very  important  factor  in 
determining  the  actual  lowering  of  water  in  the  well. 

If  we  assume  a  value  of  r  the  radius  of  a  circle,  beyond  which 
the  influence  of  the  well  will  not  be  felt,  then  the  problem  may 
be  solved.  As  a  rough  approximation,  it  may  be  assumed  that 
all  water  in  the  ground,  which  previously  flowed  past  the  cross 
section  of  the  height  of  stratum,  and  diameter  2r  given  above, 
flows  into  the  well.  Then  if  slope  of  ground  water  be  S,  the  flow 
in  the  ground  through  a  body  of  soil  of  area  27V  will  be  Q  = 
2TrKS  where  K  is  the  transmission  constant.  But 


Hence,  assuming  H,  r  may  be  found  from  the  equation 

r        HTT 

°gl°^"=  IT     gl0*' 

In  the  following,  T  =  thickness  of  water-bearing  stratum  at 
the  well,  originally  saturated  with  water. 

If  the  well  water  stands,  without  flow,  below  the  top  of  its 
stratum,  then  the  equation  of  flow  of  the  well  and  of  depres- 
sion of  ground  water  becomes 


where  T  =  thickness  of  stratum  saturated  with  water  with  no 
well  discharge. 

Integrating,        2  7r7Yi/v-7rX/r  -  Q  log  r  +  A, 
and  integrating  between  r  =  R  and  r  =  r  and  making  the  same 
assumption  as  above,  that  Q  =  2  TrKS, 
then, 


or, 


><* 


r        2TH-H2     , 
T    gl°  ~R  ~~         2TS *     gl°  *' 


WELLS.  97 

If  H  is  small  with  reference  to  T,  we  may  write  approximately, 

r      H 
r  Iog10  -  ==  -  TT  Iog10  £. 

If  there  is  no  flow  in  the  ground,  then,  obviously,  the  depres- 
sion of  the  well  will  gradually  increase  in  time,  the  rate  of 
increase  rapidly  decreasing  with  the  time. 

With  no  inflow  whatever,  the  well  will  derive  its  supply  from 
the  storage  in  the  ground,  and  as,  generally,  this  storage  is  of 
very  large  extent,  it  may  be  a  matter  of  quite  a  period  before 
the  depression  is  felt  over  any  distance.  The  well  supply  will 
come  from  the  volume  included  between  the  original  ground- 
water  plane,  and  the  plane  of  depression  of  the  ground  water. 
All  the  water  of  saturation  cannot  be  obtained,  but  assuming 
even  20  per  cent  of  this  volume  mentioned  is  available,  it 
shows  that  the  storage  capacity  of  the  soil  is  of  very  great 
importance. 

Slichter  rates  wells  at  what  he  calls  their  specific  capacity; 
i.e.j  the  flow  per  foot  the  well  water  is  lowered,  assuming  that 
the  rate  of  discharge  bears  a  constant  ratio  to  the  lowering  of 
the  water.  This  is  true  where  the  lost  head  is  lost  mainly  in 
porous  media,  but  will  not  hold  where  the  loss  of  head  in  the 
pipe  and  casing  is  considerable,  since  in  the  latter  case  the  lost 
head  varies  with  the  square  of  the  velocity.  Slichter  accord- 
ingly gives  a  formula  based  on  the  proportionality  of  head  and 
discharge  for  determining  the  flow,  from  the  time  the  well 
takes  to  fill  up  when  pumping  ceases.  The  formula  considers 
the  well  flowing  only  into  the  net  volume  of  the  casing,  deduct- 
ing plunger  rods,  etc. 

A  =  area  in  sq.  ft.  of  well  casing,  minus  the  area  of  rods 

and  pump  casing,  etc. 
q  =  Specific  capacity  or  flow  in  gal.  per  min.  per  ft.  water 

is  lowered. 

H  =  Total  head  well  is  lowered  by  pump. 
h  =  Instantaneous  depression  in  feet. 
t  =  Time  in  minutes  since  pump  stopped. 

Thus  at  any  instant  the  flow  =  qh  and  the  quantity  discharged 
in  time  dt  =  qh  dt  =  7.5  Adh. 


98  PRACTICAL  IRRIGATION. 

Hence,  integrating  between  h  —  H  and  h  =  h, 


17.25  A  fh 

Hence,  q  -      —-      Iog10     - 


Measuring  i  and  h,  and  H  and  A  being  known,  q  is  deter- 
mined. This  is  an  ingenious  method  of  arriving  at  the  flow,  but 
it  requires  to  be  accurate,  that 

1.  Practically  all  lost  head   must   be  in  the  porous  medium. 

2.  The  water  must  not  be  lowered   in  well   beyond  the  top 
of  the  water  stratum,  from  which  it  is  derived. 

3.  There  must  be  no  other  place  for  the  returning  water  to 
flow,  except  into  the  well.     In  some  cases  it  is  possible  that  there 
might  be  some  quantity  of  water  flowing  into  a  space  where  it 
would  displace  or  compress  air,  due  to  the  rise  in  pressure. 

4.  The  well  must  not  affect  neighboring  wells,  or  be  affected 
thereby,  should  they  discharge  at  the  same  time. 

Methods  and  Cost  of  Boring  Wells. 

Unlike  the  case  of  machinery  for  pumping,  it  is  impossible  to 
give  even  an  approximate  figure  on  the  cost  of  boring  or  sink- 
ing wells,  unless  the  nature  of  the  strata  encountered  be  known. 

The  best  known  form  of  well  is  the  dug  well,  where  the  sides, 
if  necessary,  are  curbed  with  wood  or  masonry,  to  prevent 
caving  of  the  earth.  These  wells  are  usually  comparatively 
shallow. 

The  drive  well  consists  of  pipe,  on  the  end  section  of  which  is 
a  strainer.  The  extreme  end  of  the  pipe  is  covered  by  a  taper 
point  which  facilitates  driving  the  pipe  into  the  ground.  These 
wells  are  usually  not  deep,  on  account  of  the  difficulty  of  driving 
the  pipe.  The  form  of  well  most  extensively  used  in  irrigation  is 
the  bored  'well. 

A  circular  hole  is  bored  in  the  ground,  by  various  means,  and, 
if  the  strata  encountered  are  liable  to  cave,  it  is  cased  off  by 
iron  casing.  Bored  wells  render  practical  the  matter  of  sinking 
to  great  depths. 


}VKLLS.  99 

The  sizes  of  bored  wells  vary  usually  from  4  inches  to  14  inches 
in  diameter. 

It  is  the  usual  practice  in  boring  wells  not  to  case  the  hole  till 
necessary.  The  following  methods  of  boring  are  in  use: 

1.  Hand  boring,  by  means  of  a  long-stem  auger,  the  debris 
being  removed  by  a  sand  pump. 

This  is  difficult  if  rock  strata  or  boulders  are  encountered. 

2.  Drop  drill.    The  material  in  the  hole  is  smashed  up  by  a 
machine-driven  drop  drill,  and  then  removed  by  a  sand  pump. 

3.  Hydraulic  sinking. 

(a)  The  bitt,  which  revolves,  is  run  by  a  hollow  pipestem 
provided  with  a  swivel  joint  on  the  top,  through  which  water  is 
forced  down  the  well,  coming  up  outside  the  pipe  carrying  the 
debris  with  it. 

This  method  is  quite  rapid  in  a  soft  soil,  frequently  one  shift 
making  40  feet  of  6-inch  hole  in  a  day. 

When  passing  through  strata  that  might  cave,  heavy  clay 
water  is  used  to  wall  up  the  strata  temporarily. 

In  sinking  6-inch  wells  in  Southern  Texas  the  pumps  supply- 
ing water  for  this  purpose  give  a  flow  of  60  gal.  per  min.  under 
35  to  40  pounds  pressure,  and  about  1500  gal.  per  day  were 
required  to  compensate  for  the  seepage  losses. 

(6)  The  well  casing  is  revolved  and  the  water  which  is 
forced  down  it  carries  the  debris  up  outside  of  it.  This  is  suit- 
able only  for  very  soft  soils,  since  the  water  does  the  cutting. 

(c)  Similar  to  (6),  except  that  the  casing  is  provided  on 
the  bottom  edge  with  a  revolving  cutter  which  makes  the  hole. 

This  is  capable  of  working  in  quite  hard  formations. 

If  it  is  necessary  to  case  the  well,  the  bottom  of  the  casing 
may  be  left  open  or  provided  with  a  strainer.  If  left  open 
(open-bottom well), it  should  stop  at  the  top  of  the  water  stratum 
and  should  not  project  into  it. 

Well  boring  is  usually  done  at  a  price  of  so  much  a  foot  for 
boring,  plus  the  cost  of  the  casing.  The  price  per  foot  depends 
on  the  size  of  the  hole,  and  it  is  usually  constant  up  to  an  even 
number  of  hundred  feet  between  200  and  500.  After  that  depth 
is  passed,  the  cost  usually  increases  at  a  given  increase  per  foot 
for  the  next  hundred  feet,  twice  the  increase  for  the  following 
hundred,  and  so  on.  For  example,  if  the  cost  is  SI .00  per  foot 
up  to  400  feet,  it  will  be,  say,  $1.10  from  400  to  500,  and  $1.20 


100  PRACTICAL  IRRIGATION. 

from  500  to  600,  etc.  Where  well  boring  is  an  established  busi- 
ness, 6-inch  wells  can  usually  be  sunk  for  from  50  cents  to 
$1.00  per  foot,  for  the  first  200  feet,  if  the  ground  is  at  all 
favorable.  With  cheap  labor,  hydraulic  rigs  and  a  soft  ground, 
wells  1000  feet  deep  can  be  bored  at  a  cost  between  $1.00  and 
50  cents  for  a  6-inch  well,  while  12-inch  wells  in  fairly  hard 
strata  from  800  to  1000  feet  deep  will  cost  from  $6.00  to  $12.00 
a  foot  for  boring,  the  cost  depending  on  the  nature  of  the 
strata. 

In  California  12-inch  wells  are  commonly  sunk  in  soft  material 
for  50  cents  per  foot  for  the  first  hundred  feet,  and  75  cents  per 
foot  for  the  second  hundred,  $1.00  per  foot  for  the  third  hundred 
feet,  and  so  on,  the  price  being  for  labor  only.  Stovepipe  casing 
is  commonly  used  in  24-inch  or  30-inch  joints.  In  shallow  wells 
single  galvanized  casing  is  used  and  is  put  on  one  joint  at  a 
time  and  riveted  up  when  set  in  place.  For  deep  wells,  however, 
double  casing  is  used,  with  inner  and  outer  joints,  lapping, 
and  the  casing  often  instead  of  being  riveted  is  simply  dented 
in  with  a  pick  at  the  joints.  This  casing  is  much  cheaper  than 
screw-joint  casing  and,  unless  the  latter  is  made  with  flush 
joints,  presents  less  resistance  in  forcing  it  into  the  ground. 
It  will  not  stand  as  much  driving,  however,  as  screw  casing,  and 
usually  is  forced  down  by  hydraulic  jacks  or  weighted  levers. 

Many  wells  are  ruined  by  improper  casing.  The  artesian 
water  is  limited  in  quantity,  and  where  the  wells  are  put  down 
without  casing  or  are  improperly  cased,  strata  of  unequal 
hydrostatic  pressure  may  be  thrown  together,  resulting  in  a  loss 
of  water  from  the  higher  pressure  stratum,  which  may  be 
seriously  injurious  to  other  wells  in  the  same  field.  It  is  a 
matter  of  public  policy  to  pass  laws  governing  the  sinking  of 
wells,  and  the  proper  casing  thereof,  to  prevent  injury  to 
neighboring  wells  and  to  endeavor  to  conserve  the  artesian 
supply  as  far  as  possible.  Wells  should  be  throttled  when  not 
in  use,  but  many  wells  are  so  poorly  cased  that  the  mere  addi- 
tional pressure  caused  by  throttling  will  open  up  a  new  passage 
for  the  water  on  the  outside  of  the  casing  and,  in  some  instances, 
the  water  will  appear  at  the  ground,  outside  the  casing,  and  in 
other  instances  it  will  force  its  way  into  other  strata,  enlarging 
the  leakage  path,  so  that  when  the  well  is  again  turned  on  the 
yield  is  diminished. 


WKLLS. 


101 


In  testing  wells,  especially  where  there  is  a  deep- well  pump  in 
the  well,  it  is  frequently  very  difficult  to  measure  the  distance 
to  water  in  the  well.  A  method  devised  by  the  author  which 
has  given  excellent  results  is  to  insert  a  small  pipe  down  the 
well  to  water.  By  blowing  down  the  upper  end  of  the  pipe  it 
is  possible  to  tell  by  the  percussion  of  the  bubbles  exactly  when 
the  pipe  enters  the  water. 

In  the  case  of  an  artesian  well  delivering  water  without 
pumping  at  the  ground  level,  the  flow  is  fixed.  With  a  pumped 
well  the  flow  may  be  varied  by  increasing  or  decreasing  the  depth 
from  which  the  water  is  drawn. 

Wells  may  be  conveniently  rated  at  the  first  cost  in  gallons 
per  minute  output.  All  wells  will  be  subject  to  a  certain  annual 
expense,  which  will  represent  the  cost  of  the  total  amount  of 
water  furnished  by  them.  In  calculations,  this  will  be  taken  at 
12  per  cent  of  the  first  cost  of  all  wells,  composed  of  7  per  cent 
interest  and  taxes,  and  5  per  cent  depreciation  and  repairs, 
the  latter  to  include  all  possible  costs  in  connection  with  the 
wells,  such  as  sand  pumping,  etc.,  as  well  as  depreciation  due  to 
deterioration  of  casing  and  falling  off  of  supply,  owing  to  increas- 
ing number  of  neighboring  wells.  The  annual  cost  of  a  well  is 
independent  of  the  amount  of  water  obtained  from  it. 

The  following  figures  were  obtained  from  results  of  a  large 
number  of  wells  in  Texas,  the  straight  average  representing  the 
mean  value  per  plant,  and  the  weighted  average  taking  the  mean 
value  of  all  the  plants  considered  as  a  unit : 

COSTS  OF  WELLS  AND  OF  WELL  WATER  IN  SOUTHERN  TEXAS. 


Artesian 
well 

Pumped 
well 

First  Cost  : 
Average  cost  per  gal.  per  min.  (straight  average)     . 

$21  .62 

$6.13 

Average  cost  per  gal.  per  min.  (weighted  average)  . 

8.30 

2.75 

Average  cost  per  acre  irrigated  (straight  average)  . 

71  .00 

15.25 

Average  cost  per  acre  irrigated  (weighted  average)  . 
Annual  cost  per  acre  irrigated  (straight  average)     .    . 

57.77 
8.63 

14.79 

*Average  cost  per  acre-foot  output  (straight  average) 

2.86 

... 

*  This  is  the  cost  of  water  actually  used  in  irrigation.     The  irrigation  factor 
was  20  per  cent. 

The  wide  difference  between  the  straight  and  weighted  average 
is  due  to  the  high  cost  of  some  of  the  small  wells.    Pumped 


102  PRACTICAL  IRRIGATION. 

wells,  in  general,  are  much  more  shallow  than  artesian  wells, 
and  hence  cost  far  less. 

It  is  a  common  belief  that  artesian  well  water  costs  nothing. 
This  is,  of  course,  erroneous,  since  even  if  the  repairs,  renewals 
and  possible  falling  off  of  water  supply  be  disregarded,  the 
interest  on  the  investment  still  runs  on.  Of  course,  it  is  highly 
desirable  to  obtain  water  without  the  operating  expense  of  a 
pumping  plant.  Still  the  first  cost  may  be  so  high  that  a  pump- 
ing plant  operating  under  low  head  may  easily  be  a  better 
investment  than  a  deep  artesian  well.  Table  L  and  curves  in 
Fig.  51  show  the  relation  between  the  irrigation  factor,  the  cost 
per  gallon  per  minute  of  artesian  wells,  and  the  cost  of  water  per 
acre-foot,  based  on  12  per  cent  annual  expense.  One  gallon  per 
minute  will  deliver  1.612  acre-feet  per  year,  and,  at  a  cost 
of  $10  per  gal.  per  min.  and  100  per  cent  irrigation  factor,  will 
cost  75  cents  per  acre-foot. 


CHAPTER  IX. 
PUMPS    AND    PUMPING    MACHINERY. 

THK  power  required  in  pumping  water  is  usually  reckoned  in 
horsepower.  One  horsepower  will  lift  3960  gals.  1  ft.  per  min., 
or  8.33  cu.  ft.  1  ft.  per  sec.  Hence,  to  find  the  actual  horse- 
power for  a  given  lift,  multiply  the  feet  vertical  lift  by  the  flow 
in  gallons  per  minute,  and  divide  by  3960,  or  else  multiply  the 
feet  lift  by  the  flow  in  cubic  feet  per  second  and  divide  by  8.83. 
The  result  is  the  net  horsepower  required  for  actual  and  useful 
work. 

In  order  to  force  water  through  suction  and  discharge  piping, 
and  around  bends,  etc.,  requires  the  expenditure  of  additional 
energy  which  must  be  furnished  by  the  pump.  The  energy  so 
required  is  equivalent  to  that  consumed  in  raising  the  water  to  an 
additional  height,  which  added  height  would  be  required  to  over- 
come all  pipe  losses.  This  added  height  is  known  as  the  head  lost 
in  the  piping,  and  may  be  calculated  when  the  sizes  of  piping,  etc., 
are  known.  Hence,  to  find  the  power  which  the  pump  must 
furnish,  the  lost  head  in  feet  must  be  added  to  the  vertical  lift 
to  find  the  total  head  against  which  the  pump  must  operate. 
Multiplying  this  head  by  the  flow,  and  dividing  by  the  appro- 
priate constant,  as  given  above,  gives  the  power  which  must  be 
furnished  by  the  pump,  known  as  the  pump  output.  The  engine 
must  deliver  to  the  pump  sufficient  power  to  supply  this  output, 
and  also  to  supply  losses  of  power  in  the  pump.  Hence,  to 
obtain  the  required  power  of  engine,  the  pump  output  should  be 
divided  by  the  pump  efficiency.  The  latter  will  range,  as  a  rule, 
from  30  per  cent  to  80  per  cent,  depending  on  the  size  and  type 
of  pump  and  on  the  conditions  of  operation.  Fifty  per  cent  is 
usually  a  safe  figure.  On  this  basis  multiply  head  in  feet  by  the 
gallons  per  minute  flow,  and  divide  by  2000,  to  get  the  horsepower 
required  to  drive  the  pump.  Table  XXVI  will  facilitate  calcu- 
lations of  this  sort. 

103 


104 


PRACTICAL  IRRIGATION. 


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IT  UPS    AND    PUMPING   MACHINERY. 


105 


Column  1  gives  ft.  lift  X  cu.  ft.  per  sec. 

Column  2  gives  ft.  lift  X  gal.  per  min. 

Column  3  gives  water  horsepower  at  100  per  cent  efficiency. 

Columns  4  to  16  give  engine  horsepower  at  various  efficiencies. 

To  lift  1  acre-foot  of  water  1  foot  requires  the  expenditure  of 
1.37  water  horsepo\ver-hours.  This  may  be  conveniently  used 
in  calculation  of  total  quantities  of  energy  required  in  the 
irrigation  of  land.  To  illustrate  the  use  of  Table  IX,  what 
horsepower  engine  must  be  provided  to  lift  700  gaL  per  min.  a 
height  of  70  feet,  the  friction  and  other  losses  in  piping  being 
20  feet,  with  a  pump  of  60 
per  cent  efficiency.  The 
total  head  is  90  ft.,  and  90 
X  700  =  63,000.  Looking 
under  the  second  column, 
6330  gal.  per  min.  X  ft. 
require  at  60  per  cent 
efficiency  2.67  horsepower. 
Hence,  required  power  of 
the  engine  =  26.6  horse- 
power. 

In  consideration  of  the 
lift  of  the  pump  there  is 
often  some  confusion  with 
regard  to  the  exact  mean- 
ing of  this  term.  Distinction 
must  be  made  between  the 
lift  of  the  pump  and  the 


Fig.  25.     Diagram  of  Pump  Lift. 


total  head  against  which  the 

pump  must  operate.  The  head  is  equal  to  the  lift,  plus  all 
the  losses  in  friction,  entrance  to  pipes,  curves,  and  discharge 
from  the  outlet  of  the  piping.  The  ratio  of  the  lift  to  the  head 
we  shall  call  the  efficiency  of  the  piping.  To  illustrate  this,  in 
Fig.  25,  let 

S    =  suction  lift 

P    =  pressure  lift 

L    =  total  lift  =  8  +  P  +  G 

H8  =  suction  head 

Hp  =  pressure  head 

H    =  total  head 


106  PRACTICAL  IRRIGATION. 

F8  =  sum  of  the  losses  of  head  occurring  in  suction  pipe 
and  in  entrance  to  the  same. 

Fp  =  loss  of  head  in  discharge  pipe,  due  to  friction,  etc. 

Gs  =  gauge  reading  of  suction  pipe,  the  suction  head 
being  considered  positive. 

Gp  =  reading  of  pressure  gauge. 

C  =  vertical  distance  from  suction-gauge  tap  to  center 
of  pressure  gauge. 

V8  =  velocity  of  flow  in  feet  per  second  in  suction  pipe 
at  the  point  of  suction-gauge  tap. 

Vp  =  velocity  in  feet  per  second  in  pipe  at  pressure- 
gauge  tap. 

V0  =  velocity  in  feet  per  second  at  discharge  end  of 
pipe. 

(V  Y 
Then,      Ha  •=  S  +  F8  +  ~^-  =  G8, 


U  1        ^         1         •*•     7)       1          ^-v  73        i         v-/       ^^          x-^ 

2^  2^ 

H8  +  Hp  -      —-  =  11  = 


All  pressures  are  in  feet  of  water.    The  efficiency  of  piping 

TT 

=  -=-  •     In  the  case  shown,  which  represents  pumping  from  a 
L 

well  or  from  a  sump,  the  meaning  of  the  term  "  lift  "  is  perfectly 
obvious,  representing  a  total  difference  of  elevation  between 
the  level  of  water  in  the  sump  of  well  and  the  level  of  the  dis- 
charge water.  However,  in  the  event  of  pumping  from  a  well 
when  the  suction  pipe  is  directly  attached  to  the  well  casing, 
the  term  "  lift  "  is  indefinite,  though  the  total  head  may  be 
defined  as  before,  as  well  as  the  suction  and  discharge  heads. 
In  selecting  a  pump,  the  head  against  which  it  must  operate, 
and  not  the  lift,  is  of  course  to  be  considered.  If  the  pipes 
where  the  pressure  and  suction  gauges  respectively  are  tapped 


PUMPS    AM)    Pl'MPINO   MACHINERY.  107 

are  of  the  same  diameter,  V,  =--  Vp,  hence  the  total   head  is 
equal  to  the  sum  of  the  gauge  readings  +  C. 

In  making  efficiency  tests  of  a  pump  care  should  be  taken 
not  to  charge  losses  in  suction  or  discharge  pipes  or  in  the 
velocity  of  discharge,  against  the  pump  itself.  These  losses 
belong  directly  to  the  piping  and  have  no  connection  whatever 
with  the  pump  efficiency.  If  the  total  lift,  L,  be  known,  the 
pipe  efficiency  may  be  calculated  from  the  data,  or  else  may  be 
measured  by  the  aid  of  gauges,  as  shown  in  the  figure.  It  should 
be  noted  that,  assuming  a  negative  pressure  in  the  suction  pipe, 
no  water  will  stand  in  the  pipe  leading  to  the  suction  gauge, 
hence  the  gauge  reading  refers  to  the  level  of  the  suction  pipe 
where  tapped.  With  reference  to  the  pressure-pipe  gauge  tap, 
however,  such  is  not  the  case,  the  pressure-gauge  pipe  being  filled 
with  water.  If  the  pressure  pipe  should  be  of  any  appreciable 
length,  care  should  be  taken  to  see  that  water  fills  the  pipe  up  to 
the  gauge,  in  order  that  air  trapped  in  the  pipe  may  not  leave 
the  actual  level  of  water  in  the  gauge  pipe  in  doubt.  Should 
there  be  a  positive  pressure  in  the  suction  pipe,  similar  pre- 
cautions should  be  taken  for  the  suction-gauge  piping.  In  this 
event,  C  would  represent  the  vertical  difference  between  gauge 
centers  instead  of  the  difference  of  level  between  center  of 
pressure  gauge  and  the  point  of  suction  tap.  Pressure  or  suction 
gauges  should  be  located  on  a  straight  section  of  the  pipe,  as 
near  the  pump  as  possible,  but  where  the  water  is  moving  at  a 
uniform  velocity.  In  case  the  head  against  which  the  pump 
operates  is  low,  particular  attention  should  be  given  to  the 
details  already  mentioned,  since,  if  disregarded,  the  same  might 
lead  to  very  large  errors  in  the  results.  In  making  accurate 
tests  of  low-head  pumps,  some  form  of  liquid  gauge  would  usually 
be  preferable  to  commercial  gauges  commonly  used.  In  reckon- 
ing the  losses  in  the  pipe,  the  friction  losses,  loss  of  head  at 
entrance  to  the  suction  pipes,  and  the  velocity  head  of  the 
discharge  pipe,  as  well  as  losses  due  to  sudden  bends  of  pipe,  or 
sudden  change  in  the  section  thereof,  must  be  computed,  in  event 
of  the  lift  alone  being  known.  To  facilitate  computation  of  this 
kind,  Table  XXVII  shows  the  losses  in  friction,  as  well  as  the 
velocity  heads  for  various  sized  pipes  delivering  water  at  different 
rates.  The  velocity  head  in  feet  is  equal  to  the  square  of  the  veloc- 
ity at  the  point  in  question  divided  by  2  g,  g  equaling  32.2.  The 


108 


PRACTICAL  IRRIGATION. 


loss  of  head  at  the  entrance  to  a  pipe  projecting  into  a  body 
of  water  is  equal  to  one-half  the  velocity  head  at  that  point 
and  the  loss  at  the  end  of  the  pipe,  where  the  same  discharges, 
equals  the  velocity  head  at  that  point. 

TABLE  XXVII. 

VELOCITY  AND  FRICTION  HEAD  TABLES  IN  NEW  CAST  IRON  PIPES. 
(Based  on  Cox's  Formula,  see  page  228,  Appendix.) 


Vplm* 

Velocity 

2-inch  pipe 

3-inch  pipe 

4-inch  pipe 

V  ClOC- 

ity 

head 

Friction 

Friction 

Friction 

Flow 

loss  per 

Flow 

loss  per 

Flow 

loss  per 

1,000  ft. 

1,000ft. 

1,000  ft. 

Ft.  per 
sec. 

Ft. 

Gal.  per 
min. 

Ft. 

Gal.  per 
min. 

Ft. 

Gal.  per 
mm. 

Ft. 

1 

.02 

10 

2.9 

22 

1.9 

39 

1  .5 

2 

.06 

20 

10.0 

44 

6.7 

78 

5.0 

3 

.14 

29 

20.4 

66 

13.6 

117 

10.2 

4 

.25 

39 

34.1 

88 

22.8 

157 

17.1 

5 

.39 

49 

51.3 

110 

34.1 

196 

25.6 

6 

.56 

59 

71.8 

132 

47.8 

235 

35.8 

7 

.76 

69 

95.5 

154 

63.6 

274 

47.7 

8 

.99 

78 

122 

176 

81  .6 

313 

61.2 

9 

1  .26 

88 

153 

198 

102 

352 

76.5 

10 

1  .55 

98 

187 

221 

124 

392 

93.5 

11 

1.88 

108 

224 

243 

149 

431 

112 

12 

2.24 

117 

264 

265 

176 

470 

132 

13 

2.63 

127 

308 

287 

205 

509 

154 

14 

3.05 

137 

355 

309 

236 

549 

177 

15 

3.50 

147 

405 

331 

270 

588 

202 

16 

3.97 

156 

460 

353 

306 

627 

230 

17 

4.50 

166 

517 

375 

344 

666 

258 

5-inch  pipe 

6-inch  pipe 

7-inch  pipe 

1 

.02 

61 

1.2 

88 

1.0 

120 

0.84 

2 

.06 

122 

4.0 

176 

3.3 

240 

2.9 

3 

.14 

183 

8.2 

265 

6.8 

360 

5.8 

4 

.25 

245 

13.7 

353 

11  .4 

480 

9.8 

5 

.39 

306 

20.5 

441 

17.1 

600 

14.6 

6 

.56 

367 

28.7 

530 

23.9 

720 

20.5 

7 

.76 

429 

38.1 

628 

31.7 

840 

27.2 

8 

.99 

489 

49.0 

706 

40.8 

960 

35.0 

9 

1.26 

551 

61.1 

794 

51  .0 

1  080 

43.7 

10 

1.55 

612 

74.8 

883 

62.2 

1  200 

53  .3 

11 

1  .88 

673 

89.5 

970 

75.7 

1320 

64.0 

12 

2.24 

734 

106 

1,059 

88.2 

1440 

75.6 

13 

2.63 

795 

123 

1,146 

103 

1560 

88.0 

14 

3.05 

857 

142 

1,235 

118 

1680 

102 

15 

3  .50 

918 

162 

1,322 

135 

1800 

116 

16 

3.97 

979 

184 

1,411 

153 

1  920 

131 

17 

4  50 

1,040 

206 

1,500 

172 

2040 

148 

*    A  XI)    PUMPING   MACHINERY. 


109 


TABLE   XXVII  —  Continued. 


IfAlxVrtffw 

8-inch  pipe 

9-inch  pipe 

10-inch  pipe 

Veloc- 
ity 

V  eiocitv 
head 

Friction 

Friction 

Friction 

Flow 

loss  per 

Flow 

loss  per 

Flow 

loss  per 

1,000  ft. 

1,000  ft. 

1,000  ft. 

I-'-.  I..T 
sec. 

Ft. 

Gal.  per 
miu. 

Ft. 

Gal.  per 

lain. 

Ft. 

Gal.  per 
min. 

Ft. 

1 

.02 

157 

.73 

198 

0.65 

245 

0.58 

2 

.06 

313 

2.5 

397 

2.2 

490 

2.00 

3 

.14 

470 

5.1 

595 

4.5 

735 

4.17 

4 

.25 

628 

8.6 

794 

7.6 

980 

6.8 

5 

.39 

784 

12.8 

993 

11.4 

1,225 

10.2 

6 

.56 

941 

17.9 

1,190 

15.9 

1,470 

14.6 

7 

.76 

,095 

23.8 

1,389 

21.2 

1,715 

19.1 

8 

.99 

,252 

30.6 

1,587 

27.2 

1,960 

24.5 

9 

1.26 

,409 

38.3 

1,786 

34.0 

2,205 

30.6 

10 

1.55 

,567 

46.7 

1,984 

41.5 

2,450 

37.3 

11 

1  .88 

,724 

56.0 

2,182 

49.7 

2,695 

44.8 

12 

2.24 

,881 

66.1 

2,380 

58.7 

2,940 

52.8 

13 

2.63 

2,037 

77.0 

2,579 

68.4 

3,185 

61.6 

14 

3.05 

2,195 

88.8 

2,777 

78.9 

3,430 

71.0 

15 

3.50 

2,350 

101 

2,976 

90.2 

3,675 

81.1 

16 

3.97 

2,507 

115 

3,175 

102 

3,920 

91.8 

17 

4.50 

2,664 

129 

3,373 

115 

4,165 

103 

11-inch  pipe 

12-inch  pipe 

13-in.  pipe 

1 

.02 

296 

0.53 

353 

0.49 

414 

0.45 

2 

.06 

592 

1.82 

707 

1.67 

828 

1.54 

3 

.14 

889 

3.71 

1,160 

3.40 

1,221 

3.14 

4 

.25 

1,185 

6.2 

1,413 

5.7 

1,655 

5.27 

5 

.39 

1,482 

9.3 

1,766 

8.5 

2,068 

7.9 

6 

.56 

1,777 

13.0 

2,120 

11.9 

2,482 

11.0 

7 

.76 

2,075 

17.3 

2,472 

15.9 

2,896 

14.7 

8 

.99 

2,350 

22.2 

2,816 

20.4 

3,310 

18.8 

9 

1.26 

2,665 

27.8 

3,180 

25.5 

3,720 

23.5 

10 

1.55 

2,964 

33.9 

3,530 

31.1 

4,140 

28.7 

11 

1  .88 

3,260 

40.7 

3,870 

37.2 

4,550 

34.4 

12 

2.24 

3,560 

48.0 

4,240 

44.0 

4,970 

40.6 

13 

2.63 

3,850 

56.0 

4,590 

51  .3 

5,380 

47.3 

14 

3.05 

4,150 

64.6 

4,950 

59.1 

5,800 

54.6 

15 

3.50 

4,450 

73.7 

5,300 

67.6 

6,210 

62.3 

16 

3.97 

4,740 

83.5 

5,650 

76.5 

6,630 

70.6 

17 

4.50 

5,040 

94.0 

6,000 

86.2 

7,040 

79.5 

110 


PRACTICAL  IRRIGATION. 


TABLE  XXVII — Continued. 


14-inch  pipe  " 

15-inch  pipe 

16-inch  pipe 

Veloc- 

Velocity 

ity 

head. 

Friction 

Friction 

Friction 

Flow 

loss  per 

Flow 

loss  per 

Flow 

loss  per 

1,000  ft. 

1,000  ft. 

1,000  ft. 

Ft.  per 

Ft. 

Gal.  per 

Ft. 

Gal.  per 

Ft. 

Gal.  per 

Ft. 

sec. 

min. 

min. 

min. 

1 

.02 

480 

0.42 

552 

0.39 

628 

0.36 

2 

.06 

960 

1  .43 

1,103 

1  .33 

1,255 

1.25 

3 

.14 

1,440 

2.92 

1,655 

2.72 

1,882 

2.55 

4 

.25 

1,920 

4.88 

2,207 

4.56 

2,510 

4.27 

5 

.39 

2,400 

7.3 

2,760 

6.8 

3,140 

6.4 

6 

.56 

2,880 

10.2 

3,130 

9.6 

3,760 

9.0 

7 

.76 

3,360 

13.6 

3,310 

12.7 

4,390 

11.9 

8 

.99 

3,840 

17.5 

3,860 

16.3 

5,020 

15.3 

9 

1  .26 

4,320 

21.8 

4,410 

20.4 

5,650 

19.1 

10 

1.55 

4,800 

26.6 

5,520 

24.9 

6,280 

23.3 

11 

1.88 

5,280 

31.9 

6,170 

29.8 

6,900 

28.0 

12 

2.24 

5,760 

37.7 

6,620 

35.2 

7,530 

33.0 

13 

2.63 

6,240 

44.0 

7,180 

41  .0 

8,160 

38.4 

14 

3.05 

6,720 

50.7 

7,730 

47.3 

8,790 

44.3 

15 

3.50 

7,200 

57.9 

8,280 

54.1 

9,420 

50.7 

16 

3.97 

7,680 

65.6 

8,840 

61.1 

10,030 

57.3 

17 

4.50 

8,170 

73.9 

9,390 

68.9 

10,680 

64.7 

18-inch  pipe 

20-inch  pipe 

22-inch  pipe 

1 

.02 

794 

0.32 

980 

0.29 

1,187 

0.26 

2 

.06 

1,588 

1  .11 

1,960 

1.00 

2,375 

0.91 

3 

.14 

2,381 

2.27 

2,940 

2.04 

3,560 

1.85 

4 

.25 

3,170 

3.80 

3,920 

3.42 

4,750 

3.11 

5 

.39 

3,970 

5.7 

4,900 

5.1 

5,940 

4.64 

6 

.56 

4,760 

8.0 

5,880 

7.2 

7,120 

6.5 

7 

.76 

5,550 

.10.6 

6,860 

9.5 

8,310 

8.7 

8 

.99 

6,350 

13.6 

7,840 

12.2 

9,500 

11  .1 

9 

1  .26 

7,150 

17.0 

8,820 

15.3 

10,680 

13.9 

10 

1  .55 

7,940 

20.7 

9,800 

18.7 

11,870 

17.0 

11 

1.88 

8,730 

24.8 

10,780 

22.4 

13,060 

20.3 

12 

2.24 

9,530 

29.4 

11,760 

26.4 

14,240 

24.0 

13 

2.63 

10,310 

34.2 

12,740 

30.7 

15,420 

28.0 

14 

3.05 

11,100 

39.4 

13,720 

35.5 

16,610 

32.3 

15 

3.50 

11,900 

45.0 

14,700 

40.5 

17,700 

36.8 

16 

3.97 

12,700 

51.0 

15,680 

45.9 

18,990 

41.7 

17 

4.50 

13,490 

57.5 

16,660 

51.7 

20,180 

47.0 

PUMPS    AND    PUMPING   MACHINERY. 


Ill 


TABLE   XXVII  —  Continued. 


24-inch  pipe 

*26-inch  pipe 

28-inch  pipe 

Ifcjr 

head 

Friction 

Friction 

Friction 

Flow 

Flow 

loss  per 

Flow 

loss  per 

1,000  ft. 

1,000  ft. 

1,000  ft. 

Ft.  per 

Ft. 

Gal.  per 

Ft. 

Gal.  per 

Ft. 

Gal.  per 

Ft. 

sec. 

min. 

mm. 

miu. 

1 

.02 

1,413 

0.24 

1,657 

0.22 

1,921 

0.21 

2 

.06 

2,827 

0.83 

3,310 

0.77 

3,840 

0.72 

3 

.14 

4,240 

1.70 

4,970 

1.57 

5,770 

1  .46 

4 

.25 

5,650 

2.85 

6,630 

2.63 

7,690 

2.44 

5 

.39 

7,070 

4.26 

8,290 

3.94 

9,610 

3.65 

6 

.56 

8,480 

6.0 

9,950 

5.5 

11,520 

5.1 

7 

.76 

9,900 

8.0 

11,600 

7.3 

13,440 

6.8 

8 

.99 

11,300 

10.2 

13,250 

9.3 

15,360 

8.7 

9 

1  .26 

12,710 

12.7 

14,910 

11.8 

17,280 

10.9 

10 

1  .55 

14,130 

15.5 

16,570 

14.4 

19,210 

13.3 

11 

1.88 

15,550 

18.6 

18,230 

17.2 

21,150 

16.0 

12 

2.24 

16,960 

22.0 

19,880 

20.3 

23,050 

18.9 

13 

2.63 

18,380 

25.6 

21,550 

23.7 

24,970 

22.0 

14 

3.05 

19,790 

29.5 

23,200 

27.3 

26,900 

25.3 

15 

3.50 

21,200 

33.8 

24,870 

31.2 

28,820 

28.9 

16 

3.97 

22,620 

38.2 

26,530 

35.3 

31,700 

32.7 

17 

4.50 

24,030 

43.0 

28,180 

39.3 

32,700 

36.9 

30-inch  pipe 

36-inch  pipe 

42-inch  pipe 

1 

.02 

2,204 

0.19 

3,180 

0.16 

4,310 

0.14 

2 

.06 

4,410 

0.67 

6,360 

0.56 

8,630 

0.48 

3 

.14 

6,620 

1.36 

9,540 

1.13 

12,94p 

0.97 

4 

.25 

8,830 

2.28 

12,700 

1  .90 

17,280 

1.63 

5 

.39 

11,020 

3.41 

15,870 

2.84 

21,580 

2.43 

6 

.56 

13,230 

4.78 

19,050 

3.98 

25,900 

3.41 

7 

.76 

15,430 

6.4 

22,230 

5.3 

30,200 

4.54 

8 

.99 

17,650 

8.2 

25,400 

6.8 

34,500 

5.8 

9 

1.26 

19,850 

10.2 

28,600 

8.5 

38,900 

7.3 

10 

1.55 

22,040 

12.4 

31,800 

10.4 

43,100 

8.9 

11 

1.88 

24,260 

14.9 

35,000 

12.4 

47,500 

10.6 

12 

2.24 

26,470 

17.6 

38,100 

14.7 

51,800 

12.6 

13 

2.63 

28,670 

20.5 

41,300 

17.1 

56,100 

14.7 

14 

3.05 

30,900 

23.7 

44,500 

19.7 

60,500 

16.9 

15 

3.50 

33,100 

27.0 

47,700 

22.5 

64,800 

19.3 

16 

3.97 

35,300 

30.5 

50,800 

25.5 

69,100 

21.8 

17 

4.50 

37,500 

34.4 

54,000 

28.7 

73,400 

24.6 

112 


PRACTICAL  IRRIGATION. 


TABLE    XXVII  —  Concluded. 


48-inch  pipe 

60-inch  pipe 

"Vcloc- 

Velocity 

ity 

head 

Friction 

Friction 

Flow 

loss  per 

Flow 

loss  per 

1 

1,000ft. 

1,000  ft. 

Ft.  per 

sec. 

Ft. 

Gal.  per 
min. 

Ft. 

Gal.  per 
min. 

Ft. 

1 

.02 

5,640 

0.12 

8,830 

0.10 

2 

.06 

11,290 

0.42 

17,650 

0.33 

3 

.14 

161,940 

0.85 

26,480 

0.68 

4 

.25 

22,600 

1.43 

35,300 

1.14 

5 

.39 

28,230 

2.13 

44,100 

1  .70 

6 

.56 

33,900 

2.98 

53,000 

2.39 

7 

.76 

39,500 

3.98 

62,800 

3.18 

8 

.99 

45,200 

5.1 

70,600 

4.08 

9 

1  .26 

50,800 

6.4 

79,400 

5.1 

10 

1  .55 

56,400 

7.8 

88,300 

6.2 

11 

1.88 

62,100 

9.3 

97,000 

7.5 

12 

2.24 

67,800 

11.0 

105,900 

8.8 

13 

2.63 

73,400 

12.8 

114,600 

10.3 

14 

3.05 

79,100 

14.8 

123,500 

11  .8 

15 

3.50 

84,700 

16.9 

132,200 

13.5 

16 

3.97 

90,400 

19.1 

141,100 

15.3 

17 

4.50 

96,000 

21.5 

150,000 

17.2 

With  low-head  plants  the  possible  losses  in  both  the  entrance 
to  the  suction  piping  and  in  the  velocity  head  lost  in  the  dis- 
charge should  be  carefully  considered,  as  they  may  easily  add 
very  materially  to  the  power  required  for  pumping.  These 
losses  can  «be  obviated  with  such  simple  and  cheap  means 
that  there  seems  little  reason  for  their  existence.  The  head 
lost  in  entrance  to  the  suction  pipe  can  be  easily  avoided  by 
belling  the  pipe  at  the  entrance.  A  bell-shaped  entrance  is 
preferable  to  a  cone-shaped,  though  the  latter  will  often  be  a 
decided  improvement  over  the  straight  pipe. 

With  reference  to  the  discharge  pipe,  a  taper  joint  with 
gradually  enlarging  section  will  overcome  almost  entirely  the 
loss  of  head  at  the  discharge.  Since  the  loss  of  discharge  head 
varies  with  the  fourth  power  of  the  diameter,  by  increasing  the 
diameter  42  per  cent,  the  discharge  loss  can  be  reduced  to  one- 
fourth  of  its  previous  value,  and  by  doubling  the  diameter,  can 
be  reduced  to  one-sixteenth  of  its  previous  value. 

It  is  no  uncommon  sight  to  find  discharge  pipes  in  irrigation 
plants  throwing  the  water  into  the  air  several  feet  above  the 


PUMPS   AND    PUMPING   MACHINERY.  113 

level  of  the  discharged  water,  owing  to  the  high  velocity  heads. 
It  is  obvious  to  even  a  casual  observer  that  this  represents  a 
considerable  loss  of  power.  Of  course  it  is  unnecessary  in  many 
cases  to  go  to  the  trouble  of  endeavoring  to  avoid  these  losses, 
provided  they  are  not  of  sufficient  importance  to  warrant  so 
doing.  From  Table  XXVII,  one  can  judge  whether  it  would 
pay  to  take  the  precautions  necessary  to  obviate  entrance  and 
discharge  losses. 

Of  recent  years  there  has  been  a  decided  increase  in  the  use 
of  irrigation  pumping  stations.  This  has  been  brought  about 
mainly  owing  to  three  reasons: 

1.  Decreased  cost  of  energy. 

2.  Improvements  in  pumps. 

3.  Settlement  of    lands  where    irrigation  is  a  commercial 
necessity.     Much  land  now  arid  can  be  successfully  irrigated 
by  pump  water,  but  the  results  of  an  undertaking  of  this  nature 
are  dependent  on  so  many  circumstances  that  a  proper  selec- 
tion of  apparatus  and  understanding  of  conditions  will  often 
tip  the  balance  from  failure  to  success. 

One  important  element  of  success  hi  many  cases  is  the  reduc- 
tion of  the  labor  required  for  the  operation  of  the  stations. 
Labor  often  forms  a  large  proportion  of  the  cost  of  pumping, 
and  any  means  by  which  it  can  be  reduced  is  of  importance. 
Skilled  labor  should  be  used  only  where  necessary,  as  much  of 
the  work  of  operation  may  be  performed  by  unskilled  workmen 
provided  there  be  a  proper  organization  and  superintendence. 

Having  determined  the  desired  capacity  of  pump  station  as 
previously  outlined,  the  next  consideration  is  the  available 
amount  of  water,  and  the  depth  from  which  it  must  be  raised, 
as  well  as  the  possible  variations  in  the  same,  due  to  dry  years, 
change  of  season,  and  the  other  plants  in  the  vicinity.  If  the 
irrigation  water  is  derived  from  wells,  most  of  this  information 
can  be  obtained  only  by  experiment,  though  often  an  approxi- 
mate idea  can  be  obtained  from  wells  near  by.  Before  going  to 
the  expense  of  installing  a  well  pumping  station,  wells  should 
first  be  tested  for  capacity. 

The  motive  power  to  be  adopted  depends  on  the  location  and 
capacity  of  the  plant,  the  required  hours  of  operation,  the  cost 
of  labor  and  fuel.  If  a  number  of  plants  are  to  be  operated  in 
the  same  vicinity,  it  may  often  pay  to  put  in  a  central  electric 


114  PRACTICAL  IRRIGATION. 

station,  and  to  distribute  energy  therefrom  to  the  various  plants, 
rather  than  to  have  each  station  provided  with  its  own  source 
of  energy.  The  distance  to  which  energy  may  be  economically 
transmitted  by  electricity,  even  in  small  quantities,  is  surpris- 
ingly large.*  As  an  illustration,  estimates  on  various  plans  for 
the  operation  of  120-stock  water  pump  stations  with  a  maximum 
probable  demand  of  90  horsepower  showed  that,  although  the  first 
cost  was  higher,  still  electrical  operation  of  the  plant  figured  out 
cheaper  than  any  other  plan.  It  involved  the  use  of  120  miles 
of  pole  line  and  of  a  complete  telephone  system.  Each  station 
was  to  contain  a  motor,  small  centrifugal  pump,  telephone,  auto- 
matic float,  operating  a  switch  for  starting  and  stopping  the 
motor,  earth  reservoir,  and  float  valves  for  letting  water  into 
the  watering  troughs.  The  plans  also  involved  a  brick  power 
house  for  generating  electricity.  The  estimated  cost  of  com- 
plete installation  was  $60,000,  or  about  $500  per  station. 

While  not  the  cheapest  system  to  install,  yet,  in  this  instance, 
the  operation  was  far  cheaper  than  by  any  other  system. 

It  would  have  been  cheaper  to  have  installed  gasoline  engines, 
but  the  operating  expense,  mainly  of  attendance,  would  have 
been  too  high  to  have  justified  such  an  installation. 

For  small  individual  pumping  plants,  requiring  a  few  horse- 
power, a  gasoline  engine  is  frequently  the  best  form  of  motive 
power.  The  oil  cups  on  the  engine  and  pump  should  be  made  of 
ample  size,  so  that  the  apparatus  can  run  for  hours  without 
attendance,  without  danger  of  accident.  For  fuel,  some  of  the 
better  grades  of  distillate  can  be  used  instead  of  gasoline,  thus 
making  a  decided  saving  in  cost.  Distillate  is  made  from  crude 
oil,  and  consists  of  the  more  volatile  parts  of  the  oil,  which  are 
driven  off  by  heat  and  then  condensed. 

Local  conditions,  of  course,  largely  govern  the  kind  of  fuel 
to  be  used,  but  the  cheapest  fuel  is  not  necessarily  the  most 
economical. 

The  expense  of  firing  and  of  handling  the  fuel  may  cut  a  large 
figure  in  the  actual  cost  of  power,  and  it  may  be  found  that  oil, 
even  if  more  expensive  than  other  kinds  of  fuel,  may  reduce  the 
operating  expenses  of  the  plant  sufficiently  to  justify  its  adop- 
tion. This,  of  course,  applies  to  stations  of  some  size,  as  with 

*  See  paper  by  the  author,  Transactions  Pacific  Coast  Transmission 
Association,  1902. 


PUMPS   AND    PUMPING   MACHINERY.  115 

smaller  stations,  which  can  be  easily  operated  by  one  man,  there 
is  no  saving  in  the  matter  of  attendance. 

There  is  such  a  wide  difference  between  the  values  of  different 
grades  of  coal  that  the  price  per  ton  should  by  no  means  deter- 
mine the  kind  to  be  used.  Some  of  the  poor  grades  of  coal  have 
not  one-third  of  the  steaming  value  of  the  better  grades,  and  they 
reduce  considerably  the  power  available  from  the  boilers,  as  well 
as  increasing  largely  the  work  of  the  firemen.  A  good  coal  will 
contain  as  high  as  14,000  British  thermal  units  per  pound,  while 
some  grades  of  poor  coal  have  less  than  5000  British  thermal 
units  per  pound. 

Among  the  various  kinds  of  pumps  and  methods  of  pumping 
in  most  common  use  in  irrigation  pumping,  may  be  mentioned 
the  following: 

1.  Deep  well  pumps. 

2.  Power  plunger  pumps. 

3.  Pumping  engines. 

4.  Direct-acting  steam  pumps. 

5.  Pulsometer. 

6.  Air  lift. 

7.  Centrifugal  pump. 

8.  Hydraulic  ram. 

1.  In  pumping  from  wells  where  the  lift  is  high,  the  distance 
to  ground  water  considerable,  the  flow  of  water  is  small,  and 
the  water  is  free  from  grit  or  sand,  the  deep- well  pump  is  usually 
to  be  preferred.     It  has  the  advantage  that  it  may  be  conven- 
iently located  inside  a  well,  thus  dispensing  with  digging  a  pit. 

2.  Power  plunger  pumps  may  be  used  to  advantage  where 
the  lift  is  high,  and  the  pump  may  be  located  so  that  it  is  not 
in  danger  of  being  submerged,  and  there  is  no  danger  of  water 
going  below  the  suction  limit. 

3.  Pumping  engines  may  be  used  to  advantage  where  the 
quantity  of  water  is  large  and  the  lift  high.     They  are  capable 
of  giving  excellent  results  for  economy,  but  their  field  is  usually 
for  city  water  works,  rather  than  for  irrigation  plants. 

4.  Direct-acting  steam  pumps,  while  possessing  the  element 
of  simplicity,  still  consume  a  large  amount  of  steam,  and  are 
quite  inefficient  in  fuel  consumption.    Their  low  first  cost  is 
usually    offset    by    increased    boiler    capacity.     Compounding 


116  PRACTICAL  IRRIGATION. 

these  pumps  results  in  a  considerable  saving  in  steam,  but  is  an 
additional  expense. 

5.  The  pulsometer,  while  simple  in   construction,  is  subject 
to  the  same  objections  as  direct-acting  pumps,  being  a  heavy 
steam  consumer. 

6.  The   air   lift,  while  not  an  efficient  method  of  pumping, 
has  still  many  advantages  for  certain  kinds  of  deep-well  pump- 
ing.    It  enables  water  to  be  drawn  from  a  considerable  depth, 
and  is  capable  of  handling  a  large  quantity  of  water  to  better 
advantage  than  can  be  done  by  a  deep-well  pump.     It  has  all 
its  working  parts  above  the  well,  easily  accessible,  and  is  not 
troubled  by  sand  and  grit  in  the  well  getting  into  the  valves. 
If  several  wells  in  the  same  vicinity  were  to  be  pumped  by  com- 
pressed air,  it  might  pay  to  install  a  central  air  station  and  to 
pipe  the  air  to  the  different  wells.     To  get  any  sort  of  efficiency 
out  of  an  air  lift  requires  a  submergence  of  the  air  pipe  at  least 
equal  to  the  lift,  and  preferably  twice  as  great. 

7.  For  pumping  plants  of  any  size,  the  centrifugal  pump  is 
generally  the  most  desirable  pump  to  install.     It  has  the  com- 
bination of  cheapness,  simplicity,  and  a  minimum  of  working 
parts.     It  has  no  valves  to  give  trouble,  and  can  handle  water 
with  grit  without  getting  out  of  order,  though,  of  course,  the 
wear  is   increased    in   that   case.     The   improvements   in  the 
centrifugal  pump  have  contributed  largely  to  the  increase  in 
irrigation  pumping.     Good  results  as  regards  efficiency  may  be 
obtained  by  the  proper  use  of  these  pumps  as  now  constructed 
by   the    leading    manufacturers.     Unfortunately,  the    laws    of 
centrifugal  pumps  are  little  understood  by  many  who  should  be 
better  informed  on  this  subject,  and  the  result  has  been  that 
many  of  them,  as  installed,  are  not  working  at  anything  like 
their  highest  efficiency.    The  proper  speed  at  which  to  run  a 
centrifugal  pump  varies  with  the  square  root  of  the  head,  the 
latter  including  both  friction  and  other  losses  of  head  and  the 
actual  lift.     The  efficient  capacity  of  a  centrifugal  pump,  when 
operating  at  its  efficient  speed,  for  a  given  lift,  varies  directly 
with  the  speed,  and   is  not  constant.      Most  centrifugal  pump 
manufacturers  make  the  serious  mistake  of  rating  their  pumps 
at  a  fixed  capacity. 

A  centrifugal  pump  can  be  rated  efficiently  at  a  given  capacity 
only  when  the  head,  and  hence  the  speed  too,  is  fixed. 


PUMPS    AND    PUMPING   MACHINERY. 


117 


8.  In  the  hydraulic  ram  the  energy  of  a  considerable  quantity 
of  water  falling  a  moderate  distance  is  made  to  force  part  of  the 
water  to  an  elevation.  The  ram  requires  very  little  attention, 
and  in  some  instances  is  quite  economical.  It  is  usually  used  in 
small  installations. 

Cost  of  Engines,  Motors,  and  Pumps. 

The  cost  of  pumping  machinery  will  vary  with  the  grade  of 
machinery  and  with  the  location  of  the  plant,  owing  to  freight 
charges.  It  is  often  desirable  to  figure  the  approximate  cost 
of  machinery  without  going  too  much  into  detail,  and  the  fol- 
lowing figures  will  give  approximate  prices. 

TABLE  XXVIII. 
COST   OF  GASOLINE   ENGINES. 


Brake 
horsepower 

Cost 

Cost  per 
horsepower 

1 

$125 

$125 

2 

225 

112 

3 

300 

100 

4 

370 

92 

5 

420 

82 

10 

640 

64 

20 

1000 

50 

50 

2200 

44 

100 

3500 

35 

Actual  prices  may  vary  from  10  to  20  per  cent  from  these  costs. 

Steam  engines  are  usually  rated  by  indicated  horsepower;  i.e., 
the  power  developed  in  the  engine  cylinder.  To  get  the  actual 
available  horsepower  output  (brake  horsepower) ,  the  mechanical 
losses  of  friction  and  windage  must  be  deducted  from  the 
indicated  horsepower.  The  mechanical  efficiency  of  engines  will 
usually  lie  between  85  and  92  per  cent.  Simple  engines  will 
cost  from  $8  to  $15  per  indicated  horsepower,  and  compound 
engines  from  $12  to  $25. 

Horizontal  tubular  boilers  will  cost  from  $6  to  $13  per  boiler 
horsepower,  and  water  tube  boilers  from  $14  to  $18  per  boiler 
horsepower. 

The  setting  for  boilers  will  cost  from  $3  to  $6  per  boiler  horse- 
power exclusive  of  foundations.  Pumps  and  heaters  will  cost  per 


118 


PRACTICAL  IRRIGATION. 


boiler  horsepower  from  $2  for  noncondensing  up  to  $5  for  con- 
densing plants.  To  these  costs  must  be  added  the  cost  of  stock, 
foundations,  pumps  and  building,  as  well  as  the  cost  of  installing 
the  plant.  As  a  rule,  irrigation  pumping  plants  of  small  or 
moderate  size  employ  cheap  engines  and  boilers,  and  hence  the 
cost  of  the  plants  will  be  nearer  the  lower  than  the  higher 
limits  given  below.  In  general,  the  use  of  compound  engines 
and  of  condensers  will  considerably  increase  the  cost  of  plant, 
though  allowing  smaller  boilers  and  more  economical  use  of  fuel. 
The  following  figures  will  give  an  approximate  idea  of  the  cost 
of  steam  plants  per  indicated  horsepower,  the  higher  limits 
representing  high-grade  machinery  not  usually  employed. 

TABLE   XXVIIIa. 
COST  OF  STEAM  PLANTS. 


Size  plant  indicated  horsepower 

5. 

10. 

25. 

50. 

100. 

200. 

500. 

Total  cost  of  steam  plant  per 
indicated  horsepower  — 
From    

$95 

75 

55 

60 

50 

47 

42 

To     

180 

160 

108 

120 

100 

90 

80 

To  these  costs  must  be  added  the  cost  of  hydraulic  develop- 
ment and  the  cost  of  irrigation  pumps. 

In  general,  irrigation  pumping  stations  will  cost  from  $60  to 
$150  per  brake  horsepower  for  plants  of  15  horsepower  and  over, 
depending  on  the  size  of  plant,  type  of  machinery,  and  cost  of 
water  development  (i.e.,  wells,  pipe  line,  or  reservoir  cost). 

The  approximate  cost  of  polyphase  induction  motors  for 
motors  of  500  volts  and  under,  is  given  in  the  following  table. 

The  actual  prices  may  vary  from  10  to  20  per  cent  from  these 
figures.  The  price  of  a  motor  will  depend  on  the  speed,  and 
will  increase  rapidly  with  decrease  of  speed. 

Centrifugal  pumps  of  the  same  nominal  size,  as  built  by 
different  makers,  have  different  capacities.  It  has  been  pointed 
out  that  it  is  wrong  to  rate  centrifugal  pumps  at  a  constant 
output  independent  of  speed,  and  that  the  proper  output  varies 
directly  as  the  speed  suitable  for  the  head.  Of  course  pumps 
if  run  at  a  sufficient  speed  will  deliver  flows  dependent  on  the 
heads  against  which  they  operate,  but  then  their  rating  should 
be  only  at  or  near  their  highest  efficiency. 


PUMPS    AND    PUMPING   MACHINERY. 


119 


TABLE  XXVIII 6. 

COST  OF  POLYPHASE   6o-CYCLE  MOTORS  FOR  VOLTAGES 
FROM   100  TO   500. 


Horsepower 

Cost 

Cost  per  hp. 

Speed  r.p.m. 

1 

$55 

$55.00 

1800 

2 

80 

40.00 

1800 

5 

100 

20.00 

1800 

10 

240 

24.00 

1200 

20 

375 

18.75 

1200 

30 

425 

14.17 

1200 

50 

600 

12.00 

900 

75 

900 

12.00 

720 

100 

1080 

10.80 

720 

150 

1500 

10.00 

580 

200 

1830 

9.15 

580 

300 

2650 

8.83 

580 

TABLE  XXIX. 

THE    APPROXIMATE    COSTS  AND    CAPACITIES    UNDER  40    FOOT 
HEAD    OF    CENTRIFUGAL    PUMPS. 


No.  Pump 

Gal.  per  min. 

Cost 

4  . 

450 

196 

6  

900 

150 

8  

1600 

220 

10  

2500 

300 

12  

4000 

380 

The  cost  of  pumping  water  may  be  regarded  as  composed  of 
three  different  parts: 

1.  Expense  for  fuel  or  energy. 

This  cost  is  generally  directly  proportional  to  the  quantity  of 
water  pumped. 

2.  Labor  expense  for  operation   of    the  plant.     This  cost  is 
generally  proportional  to  the  hours  of  operation.     However,  it  is 
in  reality  proportional  to  the  length  of  irrigation  season,  since 
generally  labor  for  operation  of  pumps  cannot  be  engaged  by 
the  day  for  the  mere  time  when  the  pumps  are  in  operation,  but 
must  be  paid  for  the  entire  irrigation  season. 

In  some  farms,  however,  the  engineer  will  do  other  work 
around  the  farm  when  the  pumps  are  shut  down  for  any  reason. 


LIBP 


t    I  K.1  •  •    .  _ 


120  PRACTICAL  IRRIGATION. 

3.  The  remaining  expenses,  while  not  strictly  of  such  a 
nature,  may  be  conveniently  regarded  under  the  head  of  fixed 
expense  bearing  annually  a  certain  proportion  to  the  total 
cost  of  the  plant. 

The  fixed  expense  may  be  segregated  under  the  following  heads : 

(a)  Interest  and  taxes. 
(6)  Depreciation. 

(c)  Repairs  and  renewals. 

(d)  Supplies  for  operation. 

(a)  Interest  and  taxes  are  independent  of  time  or  hours  of 
operation.  Seven  per  cent  of  first  cost  may  be  taken  as  a  fair 
value  for  the  same. 

(&)  Depreciation.  —  The  value  of  depreciation  is  in  part 
dependent  on  the  time  of  operation.  Without  care  machinery 
will  depreciate  as  fast  from  disuse  due  to  rusting,  as  it  will 
from  wear.  The  annual  depreciation  of  most  irrigation  plants  is 
largely  due  to  lack  of  care  and  insufficient  housing  of  machinery, 
which  is  often  left  exposed  to  the  elements. 

Depreciation  will  vary  from  about  2  per  cent  to  30  per  cent 
per  year,  depending  on  the  use  or  abuse  of  machinery;  but  8  to 
10  per  cent  should  cover  depreciation  in  most  cases,  if  reasonable 
attention  be  given  to  it. 

(c)  Repairs  and  renewals  will  vary  from  2  per  cent  to  20 
per  cent,  and  2  per  cent  should  cover  supplies  for  operation. 

With  moderate  care  the  following  figures  should  give  fair 
values  of  fixed  expenses. 

Per  cent 

Interest  and  taxes 7 

Depreciation      8 

Repairs  and  renewals 3 

Supplies 2 

20 

If  conditions  are  exceptionally  favorable,  this  figure  may  be 
as  low  as  14  per  cent.  These  figures  apply  to  the  pumping 
plant  proper.  The  total  fixed  expenses  for  pipe  lines,  wells,  and 
artificial  reservoirs  is  much  less  and  approximately  may  be  taken 
at  12  per  cent. 


PUMPS    AND   PUMPING   MACHINERY. 


121 


Hence  it  is  evident  that  the  cost  of  pumping  a  unit  quantity 
of  water  is  composed  of  the  following  three  parts: 

1.  Fuel   expense,   directly   proportional    to    the    quantities 
pumped. 

2.  Labor   expense,  directly  proportional   to  length  of    irri- 
gation season,  depending  in  part  on  the  quantity  pumped. 

3.  Fixed  expense,  independent  of  the  output  of  the  plant. 
The  proper  design  of  an  irrigation  pumping  plant  in  general 

consists  in  providing  a  plant  which  will  deliver  most  cheaply 
a  given  quantity  of  water  in  a  given  time.  To  design  a  plant 
intelligently  requires  a  knowledge  of  the  three  component 
expenses  as  well  as  the  manner  in  which  they  may  be  varied  by 
altering  the  details  of  design. 

In  general,  means  should  be  taken  to  cut  down  any  com- 
ponent of  expense  which  is  likely  to  become  unduly  large.  To 
illustrate,  if  the  fuel  expense  is  too  high,  a  more  efficient  engine 
should  be  used,  such  as  a  compound  instead  of  a  simple,  and  a 
condensing  instead  of  noncondensing. 

Should  the  labor  cost  be  unduly  high,  it  may  pay  to  install  a 
larger  plant  and  run  it  for  shorter  hours,  or  to  put  in  a  plant 
which  is  simpler  and  does  not  require  a  high  degree  of  skill  to 
operate  it. 

TABLE  XXX. 

FIRST  COST  OF   PLANTS  IN  SOUTHERN  TEXAS,  PER  WATER 
HORSEPOWER. 


Gasoline  plants 

Steam  plants 

Water 
horsepower 

Pump  plant. 

Total 

Water 
horsepower 

Pump  plant 

Total 

0.15 

$2300 

$2900 

1 

$900 

$1100 

0.3 

1700 

2160 

2 

675 

810 

0.4 

1300 

1800 

3 

525 

680 

0.5 

1100 

1530 

4 

425 

525 

0.75 

800 

1070 

5 

355 

450 

1  .00 

650 

870 

7.5 

240 

320 

1.5 

530 

730 

10.0 

160 

220 

2.0 

450 

605 

15.0 

128 

155 

3.0 

350 

500 

20.0 

110 

132 

4.0 

310 

420 

25.0 

99 

117 

5.0 

275 

370 

35.0 

85 

99 

10.0 

205 

265 

50.0 

75 

85 

15.0 

150 

190 

65.0 

72 

80 

122 


PRACTICAL  IRRIGATION. 


TABLE  XXXI. 
FUEL  CONSUMPTION  PER  WATER  HORSEPOWER  PER  HOUR. 


Steam  plants 

Gasoline  plants 

Water 
horsepower 

Wood, 
0.001  cord 

Lb.  Coal, 
10,000  British 
thermal  units 

Water 
horsepower 

Gal. 

Cost  at 
16  cents 
per  gal. 

1 

42 

31 

.2 

1  .3 

20.8 

2 

33 

30 

.3 

1  .0 

16.0 

3 

26 

29 

.4 

.84 

13.4 

4 

21 

29 

.5 

.71 

11  .3 

5 

18 

28 

.75 

.55 

8.8 

7.5 

13 

27 

1  .0 

.43 

6.9 

10 

HJ 

25 

1  .5 

.34 

5.4 

15 

11 

22 

2.0 

.33 

5.3 

20 

10J 

20 

3.0 

.33 

5.3 

25 

10 

17 

5.0 

.32 

5.1 

35 

9* 

14 

.  . 

50 

8^ 

12 

.  .  . 

75 

7 

11 

.  .  . 

... 

. 

100 

5 

10 

.  .  . 

.  .  . 

150 

4 

.  .  . 

The  average  total  cost  for  gasoline  plants,  of  gasoline,  labor,  and  fixed  ex- 
penses was  22  cents  per  water  horsepower. 


TABLE  XXXII. 

COST    OF    OPERATION    OF    STEAM    PLANTS    PER    WATER 
HORSEPOWER-HOUR. 


Water 
horsepower 

Fuel  cost, 
Cents 

Labor  cost, 
Cents 

Fixed  charges, 
Cents 

Total  cost, 
Cents 

Corresponding 
irrigation 
factors 

1 

5.7 

5.0 

2 

4.7 

3.2 

191 

27.0 

9 

3 

4.0 

2.4 

13.6 

20.0 

10 

4 

3.5 

1.8 

9.7 

15.0 

11 

5 

3.1 

1.4 

8.0 

12.5 

12 

7.5 

2.60 

.97 

7.0 

10.6 

9 

10 

2.30 

.75 

6.1 

9.2 

7 

15 

1  .92 

.54 

4.3 

6.6 

8 

20 

1.67 

.44 

2.9 

5.0 

10 

25 

1.46 

.42 

2.0 

3.9 

13 

35 

1  .18 

.42 

1.1 

2.6 

19 

50 

.96 

.42 

1  .1 

2.5 

17 

75 

.81 

.41 

1.2 

2.4 

15 

100 

.76 

.40 

1.3 

2.4 

150 

.74 

.38 

1  .3 

2.4 

PUMPS    AND    PUMPING   MACHINERY.  123 

If  the  fixed  expenses  are  too  high,  a  cheaper  type  of  plant 
should  be  installed,  or  else  a  smaller  plant  can  be  put  in  and  run 
for  longer  hours. 

The  three  sources  of  expense  are  interdependent,  and  no  system 
will  in  general  be  laid  out  properly  which  does  not  allow  and 
consider  their  quantitative  effect.  It  should  be  remembered 
that  high-grade  machinery  requires  in  general  a  more  expensive 
man  to  operate  it  than  a  simpler  and  less  expensive  type. 

To  illustrate  the  actual  results  in  practical  work,  tables  XXX, 
XXXI,  and  XXXII  have  been  compiled  from  irrigation  pump- 
ing plants  in  Southern  Texas: 

The  results  are  the  averages  of  curves  plotted  by  data  from 
over  100  plants,  and  represent,  it  is  true,  results  of  various  types 
of  plants. 

An  efficient  pumping  plant  should  better  the  results  obtained. 

All  results  are  based  on  the  actual  water  horsepower  output 
of  the  pump,  taking  thus  no  direct  account  of  pump  efficiency 
other  than  as  it  affects  the  cost  of  plant. 

The  following  are  the  existing  conditions: 

Fuel.  —  Coal  is  generally  of  poor  quality,  varying  from  4800 
to  10,300  British  thermal  units  per  pound,  averaging  perhaps 
8000.  Good  coal  goes  up  to  14,000. 

Cost  of  coal  from  SI  to  $2. 25,  averaging  about  $1.58  per  ton. 

Wood,  usually  mesquit,  about  3200  pounds  per  cord.  4500 
British  thermal  units  per  pound.  Cost,  60  cents  to  $2.50  per 
cord;  average,  $1.46. 

Gasoline,  16  cents  per  gallon. 

Labor,  mostly  Mexican,  very  ordinary  class. 

Wages,  38  cents  to  $2.50  per  day. 

Average,  about  65  cents  for  engineers. 

Fixed  expenses  for  pump  plant  proper  —  engines,  boilers, 
house  and  pump  —  are  taken  at  20  per  cent  per  year;  and  for  the 
rest  of  plant,  such  as  pipes,  reservoirs,  wells,  etc.,  at  12  per  cent. 

The  unit-water  liorsepower-hour  is  dependent  on  what  the 
plant  is  actually  doing,  and  not  on  what  it  might  do.  Engines, 
except  for  the  largest  plants,  are  simple,  noncondensing. 

It  is  to  be  noted  that  fuel  costs  are  low,  labor  is  very  low, 
but  the  fixed  expenses  are  unduly  high.  This  is  due  to  having 
too  low  an  irrigation  factor.  In  other  words,  the  plants  are  too 
large  for  the  areas  watered,  and  it  would  pay  to  take  means  to 


124 


PRACTICAL  IRRIGATION. 


avoid  making  so  large  a  first  investment  with  its  consequent 
fixed  charges.  With  gasoline  plants  of  small  capacity  no 
attendance  is  needed.  In  spite  of  the  high  cost  of  gasoline,  small 
plants  of  this  nature  are  more  economical  to  run  than  steam 
plants,  owing  partly  to  the  fact  that  they  do  not  require  constant 
watching. 

The  effect  of  the  irrigation  factor  on  the  cost  per  unit  quantity 
of  water  may  be  seen  in  the  following  case  : 

Supposing  a  plant  delivers  2  cu.  ft.  per  sec.  at  a  total  cost  per 
24-hour  day  of  $8  for  labor  and  fuel,  that  the  fixed  expenses  are 


H 

$  cost  per  acre-fl 
ft  t»i  c 

\ 

\ 

s 

^ 

KN 

Ss 

20                 ¥0                6O                6C 
perc  ent  irrigation  factor 

Fig.  26. 

$2  per  day,  Table  XXXIII  and  curve  in  Fig.  26  show  the  cost 
of  delivering  water  per  acre-foot  for  various  irrigation  factors. 
Cost  of  water  per  acre-foot  =  $2.02  for  fuel  and  labor. 


TABLE   XXXIII. 


Irrigation  factor 

Fixed  expense  per 
acre-ft. 

Total  cost  per 
acre-ft. 

5 

$10  .10 

$12  .12 

10 

5.05 

7.07 

15 

3.37 

5.59 

20 

2.53 

4.55 

25 

2.02 

4.04 

30 

1.64 

3.71 

40 

1.27 

3.29 

50 

1.01 

3.03 

75 

.67 

2.69 

100 

.50 

2.52 

Figs.  27  and  28  show  tests  of  two  of  the  New  Orleans  drainage 
pumps,  for  handling  the  city  rain  water.     The  units  are  of  the 


PUMPS   AND  PUMPING  MACHINERY. 


125 


direct-connected  vertical  type,  and  consist  of  a  centrifugal 
pump,  driven  by  a  synchronous  motor.  The  curves  are  all 
plotted  with  rate  of  discharge  in  cubic  feet  per  second  as  abscissae. 


JO    JOO 
Tn  cu.ff'Joer' sec. 

Fig.  27.     Performance  of  New  Orleans  Drainage  Pumping  Plants  a.t 
Constant  Speed. 

The  discharge  curve  shows  relation  between  flow  and  lift.  The 
kilowatt-input  curve  shows  the  relation  between  the  flow  and  the 
kilowatts-input  to  the  motor.  The  kilowatt-output  curve  shows 


¥¥0 


/80 


disch'arye  in  tu.f£  _ 

Fig.  28.     Performance  of  New  Orleans  Drainage  Pumping  Plants  at 
Constant  Speed. 

the  relation  between  the  actual  effective  kilowatts  output  of  the 
plant  in  lifting  water,  and  the  flow.  The  efficiency  curve  shows 
the  relation  between  the  ratio  of  power  output  of  water  and 
power  input  to  motor,  and  the  flow.  In  other  words,  it  shows 
the  total  efficiency  of  the  plant. 

To  illustrate  the  method  of  calculation  of  irrigation  pumping 
plants,  assume  the  following  data  for  a  plant  for  300  acres: 


126  PRACTICAL  IRRIGATION. 

1.  Depth  per  irrigation  at  the  land,  3  inches. 

2.  Frequency  of  irrigation,  once  every  10  days. 

3.  Irrigations  per  year  (no  rain),  9. 

4.  Rainfall  during  irrigation  season,  3  inches. 

5.  Pumping  plant  to  operate  12  hours  per  day. 

6.  Loss  in  ditches,  20  per  cent  of  supply. 

7.  Water  raised  by  pumping,  30  feet. 

8.  12-inch  suction  and  discharge. 

9.  200  feet  12-inch  pipe  in  both. 

10.  Centrifugal  pump,  60  per  cent  efficiency. 

Required  (a)  Capacity  pump  gallons  per  minute. 
(6)   Depth  of  water  per  season. 

(c)  Depth  of  irrigation  water  to  be  pumped  per 

season. 

(d)  Irrigation  factor. 

(e)  Total  head. 

(/)    Horsepower  to  drive  pump. 

(g)  Horsepower  hours  per  acre  per  year. 

(a)  Capacity  of  pump.  —  By  Table  II,  required  flow  =  5.7 
gal.  per  min.     Since  the  pump  operates  12  hours  per  day,  pump 

300  X  5.7  X  2 

capacity  =  -  -  =  4280  gal.  per  mm. 

O.o 

(b)  Depth  of   water  per  season  3  X  9  =  27   inches. 
Subtracting  3  inches  rainfall  leaves  24  inches  irrigation  to  be 

applied  per  year. 

(c)  Depth  of  irrigation  water  to  be  pumped  per  season. 

24 

The  pump  supply  =  —  =  30  inches,  allowing  for  ditch  loss. 
0.8 

80 

(d)  Irrigation   factor  =          ^  —  =  11  per  cent. 

obo  X  2 

(e)  Flow  of  4280  gal.  per  min.  —  by  Table  XXVII. 

Makes  loss  of  200  X  45  •*-  1000  =  9.0  feet  in  pipe. 

Loss  at  entrance 1.2     " 

Loss  at  discharge 2.3    " 

Total 1275    " 

Static  head  -.    .    .    . 30.0     " 

Total  head   .  42.5    " 


PUMPS   AND   PUMPING  MACHINERY.  127 

(/)  Power  to  drive  the  pump. 

42.5  X  4280  gal.  per  min.  =  181,900. 

Hence  at  60  per  cent  efficiency  by  Table  XXVI  the  power 
required  =  77  horsepower. 

(g)  Horsepower-hours   output  of  engine  per  acre  per  year  = 

T!|-  X  1.37  X^-X  42.5  =  242. 
12  6 

If  a  steam  plant  be  installed  with    simple    noncondensing 
engine  it  will  cost  approximately  $4800. 
Figuring  7  per  cent  interest  and  taxes, 

11  per  cent  depreciation,  repairs,  and  renewals, 
2  per  cent  operating  expense, 
20  per  cent  fixed  expenses  =  $960  per  year,  or  $3.20 

per  acre. 

If  one  man  operates  the  plant  for  the  season  of  90  days, 
receiving  $3  per  day,  the  operating  expense  is  $270,  or  90  cents 
per  acre  per  year. 

If  the  fuel  be  coal  of  12,000  British  thermal  units  per  pound, 
say  the  plant  will  require  4  pounds  per  horsepower-hour.  If 
this  costs  $6.00  per  short  ton,  the  cost  per  horsepower-hour  = 
1.2  cents,  or  $2.90  per  acre  per  year. 

Summarizing:  Fuel  cost  ....      $2.90  per  acre  per  year. 

Labor  cost 90  per  acre  per  year. 

Fixed  expenses.   .    .  3 . 20  per  acre  per  year. 
Total 7.00  per  acre  per  year. 


CHAPTER  X. 
IRRIGATION    NEAR    BAKERSFIELD. 

To  illustrate  the  actual  results  of  a  large  irrigation  pumping 
system,  the  following  account  is  given,  of  irrigation  near  Bakers- 
field. 

One  of  the  largest  irrigated  districts  of  California  is  in  the 
vicinity  of  the  city  of  Bakersfield,  which  is  situated  about  forty 
miles  north  of  the  southern  end  of  the  San  Joaquin  Valley, 
where  the  Coast  Range  and  Sierra  Nevada  mountains  unite. 
The  rainfall  in  the  surrounding  country  is  perhaps  lower  than 
in  any  other  habitable  portion  of  the  state,  being  on  an  average 
about  4  inches.  The  rain  nearly  all  falls  in  the  winter  and 
early  spring,  the  remainder  of  the  year  being  dry.  Owing  to 
the  lack  of  moisture,  much  of  the  surrounding  country  for  the 
greater  portion  of  the  time  is  barren  of  vegetation,  with  the 
exception  of  sage  brush.  The  Kern  River,  which  emerges  from 
the  mountains  about  sixteen  miles  from  Bakersfield,  is  the  only 
watercourse  of  importance  in  the  country  for  many  miles. 
After  the  river  leaves  the  mountains  it  flows  for  several  miles 
through  the  foothills,  finally  entering  the  valley  about  four 
miles  above  Bakersfield  (see  Fig.  29).  The  river  follows  the  main 
slope  of  the  country,  which  is  to  the  west,  and  somewhat  to  the 
north,  into  Buena  Vista  Lake,  an  artificial  reservoir  which  has 
been  constructed  at  the  west  side  of  the  valley  by  building 
several  miles  of  levee  to  retain  the  waters.  The  natural  dis- 
charge of  this  lake  is  towards  the  north,  to  Tulare  Lake.  The 
bed  of  the  river,  like  most  of  the  surrounding  country,  is  of  a 
sandy  nature. 

The  flow  of  the  river  is  usually  greatest  in  May  and  June,  when 
it  frequently  reaches  4000  cubic  feet  per  second  part  of  the  time, 
and  it  has  been  known  to  discharge  11,000  cubic  feet  per  second  at 
the  time  of  a  high  flood.  The  water  is  diverted  by  several  large 
canals,  the  largest  of  which  is  the  Calloway,  which  is  about  35 
miles  long,  and  has  a  capacity  of  about  900  cubic  feet  per  second. 

128 


IRRIGATION   NEAR    BAKERSFIELD.  129 

This  canal  is  80  feet  wide  on  the  base,  120  feet  on  top,  and  5 
feet  deep. 

The  water  which  is  not  utilized  in  irrigation  is  stored  in 
Buena  Vista  Lake,  which  is  about  six  miles  square,  with  a  storage 
depth  of  10  feet.  The  cost  of  the  reservoir  was  $150,000 
(Schuyler),  and  the  capacity  170,000  acre-feet  or  88  cents 
per  acre-foot,  an  exceedingly  cheap  cost  for  reservoir  con- 
struction. From  the  reservoir  large  areas  of  land  are  irrigated. 
In  good  years  there  is  an  abundance  of  water  in  the  reservoir, 
but  in  times  of  protracted  drought  it  is  entirely  without  water, 
and  the  bottom  is  absolutely  dry.  The  Kern  County  Land 
Company,  and  Miller  &  Lux,  practically  control  the  entire 
water  supply,  as  well  as  the  land,  in  this  part  of  the  country. 
These  two  companies  are  primarily  engaged  in  the  cattle  business, 
and  one  of  the  main  objects  of  the  agricultural  development  is  to 
furnish  food  for  the  cattle.  Although  other  branches  of  agri- 
culture have  been  developed,  the  greatest  part  of  the  irrigated 
land  is  planted  in  alfalfa. 

The  various  canals  owned  or  controlled  by  the  Kern  County 
Land  Company  are  all  separate  canal  companies,  each  of  which 
has  its  own  organization;  but  they  are  all  under  a  common 
management,  The  Kern  River  Canal  Company,  which  controls 
the  division  of  water  between  the  different  canals,  as  well  as 
the  distribution  to  the  various  owners.  When  water  is  scarce, 
instead  of  each  canal  receiving  its  proportion  of  water,  it  is 
all  turned  into  a  few  canals  at  a  time,  and  pro-rated  according 
to  the  water  rights  on  those  canals.  When  the  farmers  on 
these  canals  have  finished  irrigating,  the  water  is  turned  into 
other  canals,  and  in  this  manner  the  central  management 
effects  as  fair  a  distribution  of  water  as  is  possible,  and  avoids 
undue  seepage  losses  by  having  the  water  in  as  small  a  length 
of  canal  as  possible. 

In  dry  seasons  the  river  water  is  exceedingly  low,  and  con- 
sequently it  was  desirable,  if  possible,  to  install  an  auxiliary 
system  to  obtain  water  when  the  river  supply  ran  low.  The 
only  available  supply  was  the  underground  water.  There  were 
excellent  indications  of  the  possibility  of  obtaining  a  large 
supply  of  water  from  pumped  wells.  The  ground  water  level 
over  much  of  the  country  near  Bakersfield  stood  from  3  to  25 
feet  below  the  surface  of  the  ground,  the  distance  depending 


130  PRACTICAL  IRRIGATION. 

on  the  location  and  the  season.  Cheap  electric  energy  was 
available  for  the  operation  of  pumps,  as  the  Power  Develop- 
ment Company  had  its  lines  already  in  Bakersfield.  This 
company  obtained  its  energy  from  a  hydro-electric  plant  situated 
at  the  place  where  the  Kern  River  emerges  from  the  mountains. 
A  fall  of  220  feet  in  the  river  is  obtained  by  conducting  the 
water  through  a  tunnel  1.75  miles  long.  Three-phase  electric 
energy  is  transmitted  17  miles  to  Bakersfield,  under  10,000  volts 
pressure. 

The  first  pumping  station  which  was  installed  consisted  of  a 
horizontal  centrifugal  pump  belted  to  an  induction  motor.  The 
pump  was  connected  to  several  wells,  and  was  set  some  distance 
below  the  ground  in  order  to  be  as  near  the  water  level  as  pos- 
sible. Owing  to  the  variation  in  the  level  of  the  ground  water, 
there  were  objections  to  this  method  of  operation,  since,  if  the 
pump  were  set  too  low,  the  ground  water  in  some  seasons  might 
rise  until  it  covered  the  pulley.  This-  would  necessitate  pump- 
ing out  the  pit  in  which  the  pump  was  placed,  by  another  pump, 
in  order  to  lower  the  water  sufficiently  to  put  the  belt  on.  After 
the  pump  once  started,  it  would,  of  course,  keep  the  pit  dry, 
and  then  there  would  be  no  danger  unless  it  should  stop  while 
the  attendant  was  absent.  If  the  pump  were  set  up  high  enough 
to  be  out  of  danger  from  the  rising  ground  water,  it  would  be  so 
high  that  it  would  exhaust  the  wells,  and  suck  air  when  the 
ground  water  went  down  in  dry  seasons.  This  was  due  to  the 
fact  that  it  was  desirable  to  obtain  as  much  water  as  possible 
from  the  stations,  and  hence  to  exhaust  the  wells  for  several 
feet  in  depth.  In  order  to  overcome  the  difficulty  of  exhausting 
the  wells  beyond  the  suction  limit,  and  sucking  air,  which 
would  make  the  pump  lose  its  vacuum  and  stop  pumping,  a 
vertical  pump  was  installed.  The  pump  was  set  at  the  bottom 
of  a  vertical  frame,  and  was  driven  from  a  horizontal  motor  by 
a  quarter-turn  belt.  Finally,  to  avoid  the  belt  losses,  a  vertical 
motor  was  used,  direct-connected  to  the  pump. 

The  following  is  a  description  of  the  method  of  installation, 
and  the  apparatus  used  in  the  latest  stations.  The  frame  is 
20  feet  high,  and  consists  of  four  angle  irons  thoroughly  braced 
by  lighter  angles  and  united  at  the  top  to  a  cast-iron  ring  on 
which  the  motor  is  fastened.  The  top  ring  is  provided  with 
adjusting  screws  for  lining  up  the  motor.  The  pump,  which  is  a 


IRRIGATION   NEAR    BAKERSFIEL1).  131 

No.  8  centrifugal,  has  two  inlet  openings  diametrically  opposite, 
and  on  the  upper  side  of  the  runner.  The  pump  shaft  after  pass- 
ing through  a  stuffing  box  and  an  upper  bearing,  which  is  bolted 
to  the  pump  casting,  is  connected  by  a  coupling  to  the  inter- 
mediate shaft,  which  in  turn  is  connected  to  the  motor  shaft  by 
a  similar  coupling,  which  allows  of  a  longitudinal  adjustment 
of  the  pump  shaft  for  the  purpose  of  balancing.  There  is  about 
1.5  inches  end  play  in  the  pump  runner,  which  may  be  made  use 
of  in  balancing  the  end  thrust  of  the  pump,  which  is  largely 
dependent  on  the  position  of  the  runner  in  the  shell.  This  end 
thrust  may  be  very  large  in  some  pumps,  and  it  is  highly  desir- 
able that  it  be  properly  balanced,  as  otherwise  it  is  likely  to 
cause  serious  trouble.  The  intermediate  shaft  runs  in  one  or 
two  adjustable  bearings  (the  number  depending  on  the  length 
of  the  shaft).  These  bearings  are  fastened  to  the  angle  iron 
frame.  Below  each  motor  bearing,  and  fastened  to  the  shaft, 
is  a  cylindrical  brass  receptacle,  which  catches  the  oil  which 
drips  from  the  bearings.  A  stationary  bent  tube  inserted  in 
this  receptacle  catches  the  oil  clue  to  its  high  speed,  and  forces 
it  up  the  tube,  returning  it  to  the  top  of  the  bearing.  Thus  the 
oil  is  kept  in  constant  circulation. 

This  oiling  device  was  not  satisfactory,  as  it  threw  oil  all  over 
the  motor  from  the  fine  spray  which  formed.  It  was  finally 
much  improved  by  a  change  of  design  which  did  away  with  all 
trouble,  and  in  addition  passed  the  oil  through  a  filter  before 
entering  the  bearings.  The  entire  weight  of  the  rotor,  and  of 
the  pump  runner,  at  the  start  was  taken  in  the  top  motor  bearing, 
and  the  bottom  bearing  of  the  motor  limited  the  play  due  to  up 
thrust  of  the  pump  in  case  it.  was  sufficient  to  raise  the  rotor 
and  runner  both.  The  upper  bearing  of  the  motor  was  unable 
to  stand  running  with  the  weight  of  the  motor  armature  alone, 
as  it  would  have  burnt  up  under  these  conditions,  so  it  was 
necessary  to  rely  on  the  end  thrust  from  the  pump  relieving, 
in  part  at  least,  this  pressure.  The  result  in  practice  was 
satisfactory,  however,  and  gave  little  trouble.  The  suction 
entrance  on  top  of  the  runner  served  to  exert  a  strong  upward 
force,  and  by  proper  adjustment  the  pump  could  be  made  to 
balance  perfectly  and  to  lift  exactly  the  weight  of  the  revolving 
parts.  Still,  it  would  in  general  be  desirable  to  have  bearings 
better  able  to  stand  a  greater  end  thrust  without  danger. 


132  PRACTICAL  IRRIGATION. 

• 

The  usual  method  adopted  before  establishing  a  station,  was 
first  to  bore  a  6-inch  well  to  determine  the  nature  of  the  strata, 
and  to  see  whether  there  was  a  probability  of  getting  a  good 
well.  If  the  indications  were  poor,  the  site  was  abandoned. 
Twenty  feet  of  good  water-bearing  sand,  or  sand  and  gravel, 
were  considered  a  good  indication  for  a  well. 

If  the  indications  were  good,  a  13-inch  well  was  next  put 
down  and  tested  by  pumping  it  with  a  centrifugal  pump  driven 
by  a  steam  engine.  If  the  well  delivered  a  flow  of  1.5  to  2 
cubic  feet  per  second,  while  the  water  was  drawn  down  20  to 
25  feet  in  the  well,  the  test  was  considered  good,  and  three  addi- 
tional 13-inch  wells  were  put  down.  These  wells  were  all  in  a  line, 
and  about  8  to  12  feet  apart.  Riveted,  galvanized  iron  well- 
casing  was  used.  The  joints  opposite  the  water  strata  were 
perforated  before  being  put  down,  by  narrow  slits  about  an  inch 
long,  as  a  better  job  could  be  made  than  by  perforating  in  place. 
A  steel  shoe  was  fastened  to  the  end  of  the  casing,  which  was 
forced  down  by  a  weighted  lever,  while  the  material  was 
removed  from  the  inside  by  a  sand  pump.  It  was  desirable 
not  to  perforate  the  casing  too  high  up,  as  the  surface  water, 
carrying  considerable  air  and  falling  into  the  well  water  when  the 
well  was  exhausted  to  a  considerable  depth,  was  liable  to 
drag  air  into  the  suction  pipe  and  make  the  pump  lose  its 
vacuum. 

In  order  to  serve  as  an  adjunct  to  the  strainer,  and  to  keep 
sand  from  flowing  too  freely  into  the  well,  a  pipe  was  driven 
into  the  ground  next  to  the  well  casing  as  it  was  being  put 
down,  and  the  top  of  this  pipe  kept  covered  with  gravel,  which 
followed  the  well  casing  down  and  formed  a  layer  over  the 
outside  of  it. 

When  for  any  reason  it  was  impossible  to  land  the  casing  in 
clay  or  rock,  the  bottom  of  the  well  was  filled  with  loose  rock  to 
keep  the  sand  from  coming  up  the  well.  The  wells  varied  in 
depth  from  60  to  110  feet. 

After  the  wells  were  completed,  a  pit  was  dug  around  them  to 
a  maximum  depth  of  about  20  feet.  In  the  latest  stations  the 
pits  were  sunk  a  few  feet  below  the  existing  ground  water  level, 
at  the  time  they  were  put  in.  A  portable,  direct-connected 
30-horsepower  motor  and  a  No.  8  centrifugal  pump  were  used 
to  keep  the  water  out  of  the  pits  during  the  installation  of  the 


IRRIGATION   NEAR    BAKERSFIELD.  133 

station.  The  pump,  which  had  its  suction  pipe  down  one  of  the 
wells,  was  kept  running  continuously  during  the  construction 
of  the  pit. 

The  four  wells  for  each  station  were  all  in  line,  and  were 
arranged  so  that  the  vertical  pump  was  in  the  center,  with  two 
wells  on  either  side. 

The  pit  is  lined  with  redwood,  the  lower  boarding  being 
2  by  12,  and  the  upper  boarding,  1  by  12.  The  flooring,  which 
consists  of  a  double  layer  of  1  by  12,  is  laid  on  mud  sills, 
and  arranged  so  as  to  break  joints.  The  joints  on  the  sides 
of  the  pit  are  covered  with  1  by  4  battens  to  make  them 
tight  and  to  keep  the  sand  from  flowing  into  the  pit.  Inside 
the  pit,  4  by  6  vertical  stringers  are  set  3  feet  apart,  braced  by 
4  by  6  horizontal  timbers  every  6  feet.  The  pits  are  made  6 
feet  wide,  except  in  the  center,  where  they  are  8  feet  wide,  to 
allow  for  the  pump  and  frame.  The  timber  lining  of  the  pit 
was  carried  up  about  two  feet  above  the  ground,  and  the  pit 
was  covered  by  a  roofing  of  shakes. 

In  the  center  of  the  building  where  the  motor  stands,  a  house 
is  built  about  12  feet  in  height  above  the  ground,  provided  with 
a  ventilator  in  the  roof  and  also  in  the  side.  The  flooring  of 
this  house  is  level  with  the  top  of  the  pit,  and  the  top  of  the  frame 
on  which  the  motor  stands  is  slightly  above  the  floor  level.  Thus 
the  motor  is  in  a  position  where,  even  should  the  pit  fill  with 
water,  it  will  not  be  damaged.  Entrance  to  the  pit  is  provided 
by  a  door  in  the  roof,  and  to  the  motor  house  by  a  side  door. 
A  layer  of  hay  is  thrown  in  next  to  the  boarding  of  the  pit  when 
backfilling  the  outside  of  the  pit,  in  order  to  prevent  the  sand 
from  flowing  in  through  the  cracks  in  the  boards.  The  casing 
of  the  wells  is  cut  off  just  above  the  pit  floor  level,  and  is  ham- 
mered down  so  as  to  make  a  flush  joint  with  the  floor.  The 
piping  is  all  composed  of  galvanized  iron  riveted  and  soldered. 

Vertical  6-inch  pipes  about  40  feet  long  are  inserted  in  each 
well,  and  are  provided  with  flanged  couplings  to  connect  to 
horizontal  suction  pipes,  which  run  to  the  pump. 

The  discharge  pipe  is  10  to  12  inches  in  diameter  and  runs  into 
a  wooden  box  3  feet  wide,  at  the  end  of  which  is  an  uncontracted 
weir.  These  weirs  are  provided  with  glass  gauge  tubes  connected 
by  pipe  fittings  to  the  water  on  the  inside.  A  wooden  strip  is 
nailed  on  the  outside  of  the  weir  at  the  level  of  the  crest,  which 


134  PRACTICAL  IRRIGATION. 

is  composed  of  a  strip  of  galvanized  iron.  The  head  on  the 
weir  is  measured  by  a  foot  rule,  the  end  of  which  is  placed  on 
this  strip,  the  head  being  told  by  the  level  in  the  gauge  glass. 

In  the  enlarged  pit,  where  the  pump  frame  stands,  are  fastened 
square  frames  of  6  X  6  timber  surrounding  the  pump  frame. 
These  are  placed  6  feet  apart,  and  are  used  to  steady  the  pump 
frame  by  the  use  of  bolts  between  the  timber  frame  and  the 
corner  angle  irons  of  the  pump  frame. 

About  60  feet  from  the  pump  house  is  a  transformer  house 
where  the  transformer,  motor  starter,  switches  and  fuses  are 
located.  These  houses  have  been  separated,  so  that,  in  event 
of  a  fire,  the  plant  would  not  be  a  total  loss.  Energy  is  fur- 
nished to  the  transformer  houses  at  10,000  volts,  3  phase.  The 
lines  enter  the  transformer  house  passing  through  a  10,000-volt 
fused-pole  switch,  operated  by  a  lever  inside  the  transformer 
house.  Three  lightning  arresters  are  connected  to  the  10,000- 
volt  wires,  which  then  run  to  two  10,000-,  to  550-volt  trans- 
formers. 

Two  types  of  transformers  are  used  —  15-kilowatt  air-cooled 
being  in  some  stations,  and  25-kilowatt  oil-cooled  in  others. 
The  three  550-volt  wires  pass  first  through  asbestos-covered 
fuses,  the  fuse  blocks  being  mounted  with  asbestos  behind  them 
so  as  to  minimize  danger  from  fire,  and  then  through  a  knife 
switch,  and  the  auto  starter  for  the  motor,  from  which  they 
run  to  the  motor.  The  wire  joining  the  two  transformers  on  the 
550-volt  side  is  connected  to  a  static  arrester,  the  other  side  of 
which  is  grounded. 

The  lighting  circuit  is  taken  from  a  30-volt  tap  on  the  trans- 
former secondary,  the  tap  being  next  to  the  wire  connected  to  the 
arrester  to  minimize  danger  from  shock.  Thirty-  and  40-horse- 
power,  3-phase,  550-volt  motors  are  used  for  the  pumps,  which 
are  No.  8,  and  run  at  900  revolutions  per  minute,  delivering 
between  3  and  5  cubic  feet  per  second,  depending  on  the  lift, 
the  usual  head  being  40  feet. 

As  the  stations  were  to  be  operated  with  little  attendance, 
it  was  necessary  to  make  everything  about  them  as  safe  as 
possible  from  the  effect  of  possible  accident.  With  this  in 
view,  each  station  was  provided  with  an  automatic  cut-out,  to 
cut  out  the  motor  in  case  the  power  went  off.  For  this  purpose 
a  heavy  weight,  sliding  in  ways,  was  hooked  to  the  switch  handle. 


IRRIGATION    NEAR    BAKERSFIELD.  135 

This  weight  was  released  by  a  trigger,  and  thus  required  very 
little  power  to  make  it  open  the  switch.  Several  devices  were 
used  to  operate  the  trigger,  the  particular  form  depending  on 
the  conditions  of  the  case.  In  a  transmission  system  there  is 
always  the  liability  of  a  momentary  short  circuit,  caused  by  a 
discharge  of  the  lightning  arresters,  or  by  some  other  cause, 
making  the  voltage  drop  for  only  a  few  instants.  In  such  an 
event  it  is  not  desirable  for  the  cut-out  device  to  operate,  and  it 
must  be  designed  with  that  in  view.  The  form  most  commonly 
used  consisted  of  a  vertical  tank  in  which  was  a  float  provided 
with  a  vertical  stem  engaging  the  trigger.  This  tank  received 
its  pressure  from  a  point  near  the  pump  discharge,  the  water 
standing  at  a  level  above  the  crest  of  the  weir  equal  to  the 
head  on  the  wreir  plus  the  friction  head  in  the  pipe.  If  the 
pump  stopped,  the  float  would  gradually  sink  until  it 
tripped  the  weight,  but  a  temporary  slowing  down  would  not 
affect  it. 

Another  device  consisted  of  a  curved  vane  in  the  discharge 
pipe,  supported  by  pins,  one  of  which  extended  through  a 
stuffing  box  and  operated  the  trip  lever  through  a  bell-crank 
lever.  When  water  was  flowing  it  kept  the  vane  along  the 
pipe  where  it  offered  little  additional  fractional  resistance,  but 
when  it  ceased  to  flow,  the  weight  of  the  vane  tripped  the  switch- 
opening  weight. 

Time  element  electric  devices  have  also  been  used.  These 
consisted  of  a  laminated  electromagnet,  the  armature  of  which 
was  kept  closed  by  30- volt  alternating  current.  In  one  form 
of  device  there  was  a  glycerine  dashpot  connected  to  the  arma- 
ture, there  being  a  small  hole  in  the  piston  to  allow  of  slow 
motion.  If  the  power  went  off  and  came  on  again  before  the 
piston  sank  too  far,  the  armature  would  be  reattracted  before 
the  switch  had  opened.  In  another  form  the  retarding  element 
consisted  of  a  small  fan  blade  connected  to  the  armature  by 
clockwork. 

In  general,  the  first  two  forms  are  more  desirable,  where  they 
can  be  used,  since  if  for  any  reason  the  pump  loses  its  priming, 
they  will  rut  out  the  motors. 

With  regard  to  piping  leading  to  the  float  boxes,  for  the  first 
form,  it  is  advisable  to  use  in  general  galvanized  pipe,  and  not 
to  use  too  small  a  pipe,  on  account  of  danger  of  the  pipe  rusting 


136  PRACTICAL  IRRIGATION.' 

up  and  stopping.  This  is  important,  particularly  where  the 
water  is  alkaline. 

As  there  was  in  some  cases  a  considerable  volume  of  piping  to 
prime  before  starting  the  pump,  priming  by  hand  was  too  slow, 
so  air  pumps  were  installed  in  the  pits,  belt-driven  from  the 
motor  shaft.  When  the  pump  was  primed  the  belt  was  taken 
off.  This  saved  considerable  time  in  starting  the  stations,  and 
pumps  which  took  half  an  hour  to  prime  by  hand  could  be 
primed  in  a  few  minutes  in  this  manner.  Check  valves  and 
sometimes  gate  valves  were  placed  just  above  the  discharge 
outlet  of  the  pump,  to  close  the  pipe  for  priming.  In  some 
stations  when  they  had  not  been  run  for  considerable  time,  the 
water  carried  a  large  amount  of  entrained  air,  which,  if  the  pump 
were  run  with  the  discharge  open,  would  be  liable  to  make  the 
pump  lose  its  priming.  For  these  stations  the  gate  valves  were 
a  decided  aid  in  operation,  as  they  could  be  used  to  throttle 
the  discharge,  as  long  as  there  was  any  trouble  of  this  nature. 

Fig.  29  is  a  map  of  the  pump  stations  of  the  Kern  County 
Land  Company.  There  are,  altogether,  27  well-pumping  stations 
scattered  over  a  considerable  area  denoted  by  small  squares  and 
numbers  along  the  lines  of  the  Power  Development  Company. 
This  was  divided  into  three  sections,  and  one  pump  man 
assigned  to  each  section.  These  three  pump  men  attended, 
alone,  to  the  operation  of  all  the  plants,  visiting  each  station 
in  operation  twice  a  day.  Each  pump  man  was  provided 
with  a  horse  and  cart.  In  addition  the  operation  of  the  plants 
required  part  of  the  time  of  an  inspector,  who  had  charge  of 
all  repairs  and  installation  work,  and  the  services  of  his  assist- 
ants. The  pump  men,  who  were  not  skilled  mechanics,  were 
expected  to  attend  to  merely  the  operation  of  the  stations  and 
to  report  any  repairs  needed.  When  in  operation  the  stations 
ran  continuously  day  and  night,  and  were  shut  down  only  a  very 
small  proportion  of  the  time.  Thus  it  will  appear  that  the  cost 
of  operation  was  reduced  to  a  minimum  —  quite  a  striking 
contrast  to  the  method  of  operation  adopted  in  some  pump 
stations,  where  three  men  working  8-hour  shifts  are  employed 
every  day  to  watch  one  30-horse  power  motor  and  pump 
operate. 

It  may  occasion  doubt  in  the  minds  of  many  whether  such  a 
method  of  operating  is  wise,  and  whether  it  is  not  taking  undue 


IRRIGATION   NEAR    BAKERSFIELD. 


137 


chances  of  loss  from  accident  from  no  attendant  being  at  hand. 
The  experience  of  the  writer  is  quite  to  the  contrary.  In  fact, 
the  total  loss  from  accidents  which  could  have  been  avoided  by 


constant  attention,  would  not  exceed  a  few  hundred  dollars 
during  the  writer's  connection  of  two  years  with  the  company. 


138  PRACTICAL  IRRIGATION. 

No  serious  accident  occurred  during  that  time,  the  only  damage 
being  the  burning  out  of  an  occasional  bearing.  The  secret  of 
success  in  such  a  matter  consists  in  keeping  the  plant  always 
in  the  best  order,  occasional  overhauling,  and  constant  watch- 
fulness. 

The  pumps  discharged  into  the  same  canals  used  by  the  gravity 
system,  and  consequently  there  is  no  direct  means  of  obtaining 
a  record  of  the  value  of  the  irrigation.  Further,  as  they  were 
used  only  to  supplement  the  river  water,  the  duration  of  their 
operation  during  the  year  was  a  variable.  Had  they  been  used 
as  the  sole  source  of  water  supply,  they  would  have  run  nearly 
continuously  throughout  the  year,  in  a  climate  like  that  of 
Bakersfield  with  its  very  small  rainfall.  Of  the  river  water, 
one-third  of  the  total  water  supply  is  lost  in  the  canals.  It 
takes,  on  an  average,  1  acre-foot  of  water  supplied  to  the  canals, 
for  the  irrigation  of  1  acre  of  land  per  irrigation.  The  pumped 
water  has  far  shorter  distances  to  travel  than  river  water. 
Allowing  for  the  effect  of  a  decreased  quantity,  and  greater 
relative  seepage  losses,  it  will  be  conservative  to  say  that  it 
takes  1  acre-foot  of  pumped  water  to  irrigate  an  acre  of  land. 
Land  is  irrigated  once  per  cutting  for  alfalfa,  and  yields  an 
average  crop  of  one  ton  per  acre.  Hence  1  acre-foot  of  pumped 
water  is  needed  per  ton  of  hay,  and  4  acre-feet  per  acre  are 
required,  per  year,  as  four  crops  are  grown  in  a  year. 

The  average  output  of  the  pump  stations  was  3.3  cubic  feet 
per  second.  This  average  was  cut  down  to  this  value  by  some 
poor  stations  where  the  wells  were  weak.  The  average  motor 
horsepower  per  station  was  33.  Energy  was  bought  accord- 
ing to  the  horsepower  of  the  motor  installed,  and  with  no 
reference  to  the  load,  the  price  paid  being  five-eighths  cent  per 
horsepower-hour.  Hence  the  cost  of  energy  per  10  horsepower- 
day  was  —  X  7—  =  $1.50,  which  was  the  cost  per  second  foot  of 
o  10U 

water  per  day.  Hence  the  cost  per  acre-foot  was  75.7  cents 
for  energy  alone,  or  double  the  cost  charged  for  gravity  water 
by  the  canals.  The  remaining  expenses,  including  wages, 
repairs,  and  all  fixed  expenses,  were  practically  constant,  and 
were  independent  of  the  hours  of  operation  of  the  plant.  In 
estimating  the  fixed  expenses,  7  per  cent  is  assumed  for  interest 
and  taxes,  6  per  cent  for  depreciation.  The  total  cost  of  the 


IRRIGATION   NEAR    BAKERSFIELD.  139 

27   stations,   including   the   cost   of   abandoned   stations,    was 
$92,000,  nearly  4  per  cent  of  which  was  for  abandoned  stations. 
The  total  annual  expenses  were  as  follows: 

Fixed  expenses,  13  per  cent  of  $92,000  .  811,960  per  year. 

Cost  of  attendance 2,477  "       " 

Cost  of  maintenance 3,035  "       " 

Cost  of  repairs  and  renewals     ...        .         3,419  "       " 

Total  annual  expenses $20,891  "      " 

The  actual  expense  for  attendance  was  for  the  27  plants, 
$:M77  per  year,  or  $91.75  per  station,  or  25  cents  per  station  per 
day.  This  included  wages  and  board  of  the  attendants,  feed 
for  their  horses,  and  repairs  on  their  wagons.  This  is  an  excep- 
tionally low  figure,  and  it  is  very  doubtful  if  any  stations  of 
equal  capacity  ever  came  anywhere  within  several  hundred 
per  cent  of  these  figures. 

The  charges  for  maintenance  included  the  time  of  the  pump 
inspector  and  his  two  helpers  in  ordinary  overhauling  of  the 
stations,  and  also  all  supplies  for  operation,  such  as  oil  waste,  etc. 
The  charge  for  repairs  included  a  $1700  charge  for  the  recon- 
struction of  one  of  the  first  experimental  stations  installed. 
The  peculiar  conditions  encountered  made  this  reconstruction 
a  very  expensive  piece  of  work,  and  one  which  was  little  likely 
to  recur.  However,  work  of  reconstruction  as  well  as  the 
danger  of  accident  must  always  be  considered  in  fixing  costs. 
Included  under  repairs  and  renewals  were  certain  improvements 
which  more  properly  belonged  under  installation.  Taking  this 
into  consideration,  the  charge  of  6  per  cent  for  depreciation  is 
a  liberal  value,  as  the  repairs  and  renewals  are  nearly  4  per 
cent.  A  very  large  part  of  the  charges  for  maintenance  and 
repairs  consisted  in  team  hire,  and  time  lost  in  getting  around 
the  country,  owing  to  the  widely  scattered  stations. 

The  total  charge  of  $8931  per  year  which  actually  had  to  be 
paid  out,  was  only  91  cents  per  day  per  plant.  If  the  plants 
ran  continuously  they  would  have  raised  177  acre-feet  per  day, 
or  177  X  365  =  64,500  acre-feet  per  year,  at  a  cost  of  33.2  cents 
per  acre-foot  for  fixed  charges;  or  a  total  cost  of  75.7  +  33.2  = 
$1.09  per  acre-foot.  During  the  last  part  of  the  year  in  question, 
the  pumps  ran  only  34  per  cent  of  the  total  time,  making  the 
expense  of  all  charges  but  power,  per  acre-foot,  98  cents,  and  the 


140  PRACTICAL  IRRIGATION. 

total  cost  SI. 74  per  acre-foot,  and  hence  per  ton  of  hay.  This 
was  an  exceptionally  low  irrigation  factor,  and  was  due  to  the 
fact  that  owing  to  accidents  the  Power  Development  Company 
had  been  unable  to  furnish  energy  for  the  operation  of  the  pumps. 

During  the  first  six  months  of  the  year  when  energy  was 
obtainable,  the  pumps  ran  about  90  per  cent  of  the  time,  though 
no  record  was  kept  of  the  same,  as  at  that  time  energy  was  paid 
for  on  a  flat  rate  of  $30  per  horsepower-year  for  the  first  100 
horsepower,  $25  per  horsepower-year  for  the  second,  and  $20 
per  year  for  all  additional  horsepower.  Under  those  con- 
ditions the  annual  cost  of  energy  for  33  X  27  =  991  horsepower 
was  $19,320,  which  is  29.9  cents  per  acre-foot,  assuming  100  per 
cent  irrigation  factor,  or  33.2  cents,  assuming  90  per  cent  irri- 
gation factor.  Adding  to  this  latter  figure  the  corresponding 
rate  of  37  cents  for  fixed  and  operating  charges,  gives  a  total 
cost  per  acre-foot  of  70  cents. 

Hence,  owing  to  change  of  rates  and  conditions  in  the  same 
year,  the  cost  of  water  went  from  70  cents  to  $1.74  per  acre-foot. 
With  90  per  cent  irrigation  factor  and  five-eighths  cent  per  horse- 
power-hour, the  cost  would  be  $1.13  per  acre-foot.  The  value 
of  a  ton  of  hay  in  the  field  is  fully  $4.  Under  the  system  of 
charging  by  the  rated  motor  horsepower,  a  far  more  economi- 
cal showing  could  be  made  by  installing  much  smaller  motors 
in  the  stations  where  the  wells  were  weak.  As  the  pumps  gave 
an  efficiency  of  60  per  cent,  they  were  capable  of  lifting  on  an 
average  lift  of  40  feet,  4.4  cubic  feet  per  second;  the  30-horse- 
power  motors,  4  cubic  feet  per  second,  and  the  40-horsepower 
motors,  5.3  cubic  feet  per  second.  The  actual  output  of  plants 
went  from  1.6  to  5.7  cubic  feet  per  second,  and  the  lifts  from  30  to 
50  feet.  The  efficiency  of  a  pump  in  practice,  when  operating 
under  a  high  vacuum,  will  usually  be  less  when  pumping  from 
a  well  than  when  pumping  from  a  pond,  due  to  the  entrained 
air.  Mr.  L.  A.  Hicks  was  the  first  engineer  in  charge  of  the 
installation  of  the  pumping  plants,  and  was  succeeded  later  by 
the  author. 


CHAPTER  XI. 
METHODS    OF    CHARGING    FOR    IRRIGATION    WATER. 

THERE  are,  in  general,  three  systems  of  charging  for  irrigation 
\vuter,  at  present  in  use: 

1.  Where  no  particular  limitation  is  placed  on  the  water, 
contracts  simply  stating  that  the  farmer  will  be  provided  with 
sufficient  water  to  irrigate  his  land;  2.  where  he  will  be  pro- 
vided with  a  stated  flow  for  a  stated  length  of  time,  distributed 
at  stated  periods  at  a  stated  annual  rate;  3.  where  the  charge 
for  water  is  directly  proportional  to  the  amount  of  water  used. 

None  of  these  systems  is  in  general  altogether  equitable, 
since  it  does  not  proportion  the  expense  for  \vater  to  the  cost 
of  delivering  the  same.  The  best  system  of  charges  should 
fulfill  three  conditions:  1.  It  should  proportion  the  charges  to 
the  expense  of  delivery.  2.  It  should  induce  economy  on  the 
part  of  irrigators.  3.  It  should  be  simple. 

Consideration  of  No.  1  requires  an  analysis  of  the  elements 
of  the  cost  of  furnishing  water.  Take,  for  example,  the  case  of 
an  irrigation  company  furnishing  pumped  water  to  its  custom- 
ers. For  the  company  to  be  in  position  to  supply  water  for 
irrigation,  it  must  first  provide  a  pumping  station,  ditches,  gates, 
etc.,  all  of  which  are  in  proportion  to  the  sum  of  the  maximum 
rates  of  demand  of  the  water  supplied  to  customers.  Before 
starting  to  deliver  water  to  consumers  the  plant  must  be  operated 
to  a  sufficient  point  to  supply  losses  in  the  canals.  Up  to  that 
point  of  operation  the  individual  guaranteed  rate  of  supply  is 
a  measure  according  to  which  the  expenses  should  be  divided. 
Additional  expense  of  operation  of  the  plant  beyond  this  point 
will  consist  mainly  of  fuel  and  labor,  and  will  be  proportional  to 
the  actual  quantity  of  water  used ;  hence  all  expenses  beyond  this 
point  of  operation  should  be  divided  in  proportion  to  the  actual 
quantity  of  water  consumed.  In  other  words,  an  equitable 
policy,  to  fulfill  condition  No.  1,  would  consist  of  charging  each 
consumer  of  water  a  fixed  rate  with  a  guaranty  to  supply  him 

141 


142  PRACTICAL  IRRIGATION. 

with  such  a  flow  for  a  given  length  of  time  every  so  many  days, 
and  in  addition  should  charge  a  rate  directly  proportional  to 
the  actual  amount  of  water  used.  Such  a  system  would  tend 
to  promote  economy  in  the  use  of  water,  as  it  is  directly  to  the 
financial  advantage  of  the  irrigators  to  practice  it.  Moreover, 
it  is  a  fair  basis  of  division  of  the  charges,  and  it  is  only  right 
that  the  farmer  who  is  economical  should  not  pay  for  the 
extravagance  of  his  neighbor.  In  some  places,  usually  where  no 
limitation  is  placed  on  the  irrigation  water,  the  payment  for  the 
same  consists  of  a  certain  percentage  of  the  crop.  This  method 
of  charging  has  the  advantage  of  attracting  people  with  small 
capital.  However,  it  sometimes  occasions  disputes,  and  is  liable 
to  give  rise  to  a  suspicion  that  the  farmer  has  not  reported 
the  full  amount  of  his  crop.  Of  course  the  manager  of  an  irri- 
gation company  has  to  consider,  in  addition  to  charging  for 
furnishing  water  on  an  equitable  basis,  the  idea  of  presenting  an 
attractive  prospect  in  order  to  settle  the  country  and  to  obtain 
customers.  This  may  be  used  as  an  argument  in  favor  of  the 
percentage  of  the  crop  basis  of  charging,  on  the  ground  that  this 
system  would  attract  those  who  would  not  otherwise  enter  into 
the  undertaking.  A  careful  consideration  of  the  actual  cost  to  an 
irrigation  company  for  the  delivery  of  water  indicates  that  the 
charges  for  same  should  be  divided  among  customers  in  accord- 
ance with  a  method  embracing  the  three  following  principles: 

1.  Expense  which  should  be  borne  equally  by  the  consumers. 

2.  Charges  pro-rated  according  to  the  maximum  required  flow. 

3.  Charges  proportional  to  the  volume  of  water  actually  used. 
Charges  of  the  first  nature  may  be  considered  to  include  general 
expenses  of  the  company  as  well  as  the  expense  of  zanjeros* 
Under  the  second  heading  may  be  classed  the  charges  which  are 
independent  of  the  water  actually  delivered;    in  other  words, 
charges  of  this  nature  should  be  for  the  cost  to  the  ditch  com- 
pany of  being  in  a  position  to  deliver  water  at  a  certain  rate. 

Charges  of  the  third  kind  are  dependent  upon  the  cost  to  the 
company  of  actually  delivering  a  given  quantity  of  water. 

In  a  pumping  plant,  for  example,  the  capacity  of  the  station 
would  have  to  be  proportioned  to  the  maximum  rate  of  demand 
for  water;  hence  all  expenses  for  operating  the  plant  to  a  sufficient 
point  to  supply  the  seepage  losses  in  ditches  and  for  interest  and 

*  Zanjero  is  the  Mexican  name  for  ditch  tender. 


CHARGING   FOR   IRRIGATION   WATER.  143 

depreciation  on  the  plant,  should  be  pro-rated  according  to  the 
maximum  rates  of  demand  of  the  various  customers.  The 
annual  value  of  the  water  right,  if  the  same  has  any  value,  should 
also  be  pro-rated  in  the  same  manner,  as  well  as  the  interest  on 
and  cost  of  maintenance  of  ditches,  gates,  etc.  The  additional 
cost  of  delivery  of  water  over  what  would  be  necessary  to  keep 
the  ditches  full  and  in  repair,  should  be  borne  by  the  customers 
in  direct  proportion  to  the  quantities  of  water  actually  used. 
This  would  mean,  in  other  words,  that  a  customer  of  the  com- 
pany would  pay  the  company  a  certain  fixed  sum  for  the  privilege 
of  obtaining  water,  and  in  addition  thereto  a  sum  varying 
directly  with  the  rate  of  use  of  water  which  the  company  guaran- 
tees to  furnish.  In  event  of  any  shortage  of  water,  this  latter 
rate  would  not  be  the  same,  but  the  water  would  be  delivered 
among  the  various  customers  in  proportion  to  the  rates  of 
delivery  for  which  they  pay.  Besides  these  two  charges,  the 
customer  would  pay  a  rate  proportional  to  the  actual  volume 
of  water  delivered  to  him.  In  fixing  the  rate  of  charge  at  a 
given  rated  delivery,  a  reasonable  amount  of  time  should  be 
taken.  For  example,  provided  the  consumer  uses  a  flow  of  3 
cubic  feet  per  second  for  one  day  a  week,  the  flow  for  which  he 
should  be  charged  would  be  three-sevenths  of  1  cubic  foot  per 
second.  In  other  words,  the  flow  should  be  reduced  to  the  basis 
of  a  maximum  continuous  flow,  and  should  not  be  considered 
as  a  maximum  absolute  flow.  A  contract  for  water  would 
then  state  that  the  consumer  was  entitled  to  a  certain  specified 
flow  delivered  for  a  specified  number  of  hours  once  every  so 
many  days,  for  which  he  would  pay  a  specified  rate  per  month, 
whether  or  not  use  was  made  of  this  quantity  of  water;  and  in 
addition  would  pay  a  fixed  rate  per  acre-foot  of  water  delivered. 
This  would  make  it  to  the  advantage  of  the  consumer  to  apply 
for  as  small  a  flow  as  possible  and  to  use  the  water  as  economi- 
cally as  possible,  both  of  which  are  desirable  features  in  the 
practice  of  irrigation.  If  during  the  course  of  the  year  the  con- 
sumer found  he  would  need  more  water  than  the  flow  for  which 
he  had  contracted,  if  this  water  were  available  he  could  obtain 
it  by  paying  for  it  at  the  fixed  rate  per  acre-foot. 

This  method  of  charging  for  water  might  lead  to  a  tendency 
to  reduce  the  flow  applied  for  to  a  quantity  too  small  for  the 
needs  of  the  land,  in  order  to  reduce  the  charges  under  the 


144  PRACTICAL  IRRIGATION. 

second  head,  consumers  relying  upon  being  able  to  obtain 
surplus  water  at  the  price  charged  per  acre-foot.  However, 
by  so  doing  they  would  render  themselves  liable  to  suffering 
from  possible  shortage  in  supply,  and  steps  could  easily  be  taken 
by  the  company  to  prevent  this  becoming  an  abuse. 

In  considering  the  proportions  of  the  constituent  parts  of 
these  three  charges,  three  distinct  cases  may  be  taken  up: 
1.  Gravity  distribution  without  storage.  2.  Storage  system 
of  distribution.  3.  Pumping  distribution. 

In  the  gravity  system  the  largest  charge  would  be  for  the 
guaranteed  flow  of  water,  the  total  amount  of  water  used  making 
little  difference  in  the  cost  to  the  company. 

In  case  No.  2,  assuming  an  expensive  reservoir  system  from 
which  the  water  is  mainly  supplied  by  storage,  the  charge  for 
the  quantity  of  water  actually  used  becomes  comparatively 
great,  since  the  interest  on  the  investment  in  the  reservoir, 
repairs,  and  depreciation  of  the  same  are  chargeable  to  the 
value  of  an  acre-foot  of  water. 

In  case  No.  3,  the  additional  cost  of  fuel  and  labor  contributes 
largely  to  charge  No.  3.  Let : 

A  =  Annual    interest,    depreciation,   repairs   and   taxes   on 

reservoir. 

B   =  Total  annual  value  of  water  right. 
C   =  Annual  value  of  water  lost  in  distributing  canals. 
D  =  Labor  and  interest  on,  and  repairs,  and  depreciation  of 

main  and  distributing  canals. 
E  =  Annual  cost  of  zanjeros. 
F  =  General  expenses. 
G  =  Interest  and  depreciation  on  power  house,  head  works, 

labor,  operating  expenses,  and  cost  of  fuel  sufficient 

to  supply  seepage  losses  of  canals. 
H  =  Additional  annual  expenses  of  power  house  required  for 

operation  of  plant  at  capacity  demanded. 
N  =  Number  of  customers. 
P  =  Maximum  rate  of  consumption  of  water. 
p    =  Individual  rate  of  consumption. 
Q  =  Acre-feet  stored    less    evaporation    and    seepage    from 

reservoir  =  total  acre-feet  of  reservoir  output,  or  = 

output  of  pump  station. 


CHARGING   FOR   IRRIGATION    WATER.  145 

q  =  Acre-feet  sold  to  individuals. 

X  =  Acre-feet  lost  in  distributing  canals. 

Assuming  case  No.  2,  where  practically  all  the  water  is  stored 
and  must  be  taken  from  a  reservoir,  the  following  three  charges 
should  be  made: 

E  4-  F 

— — —  should  be  charged  alike  to  each  applicant  for  water, 

as  charge  No.  1. 

AX 


//?  -4-  C1  -\-  D\ 

I-     — - — —    -\p  =  charge  No.   2,   where   C  = 

An 

=  charge  No.  3. 


()  -X 

Suppose  the  water  for  irrigation  is  supplied  direct  to  the  land 
from  a  pumping  station,  then  charge  No.  1  would  be  the  same 
as  in  the  last  case. 

p  =  charge  No.  2,  charge  C  being  included 
in  G. 

charge  No.  3. 

--    A 

These  cases  will  serve  to  illustrate  the  general  method  sug- 
gested,—  which  is  similar  to  a  method  of  charging  for  electric 
energy,  proposed  by  Mr.  A.  M.  Hunt, —  and  form  a  basis  from  which 
equitable  charges  for  water  may  be  made.  In  proportioning 
the  charge  for  the  water  itself,  the  assumption  has  been  made  that 
the  value  of  the  water  per  se  lay  in  the  broader  right  to  utilize 
a  given  flow  of  water,  and  not  in  the  intrinsic  value  of  the  water 
itself.  This  is  true  on  the  assumption  that  water  not  so  util- 
ized would  have  no  market  value.  If,  on  the  other  hand,  how- 
ever, such  water  has  a  market  value  per  se,  then  the  real  value 
of  the  water  becomes  of  two  kinds:  (1)  the  value  of  the  water 
right  itself,  and  (2)  the  intrinsic  value  of  the  water.  In  this 
event  the  latter  value  should  be  added  to  the  charge  for  water. 
Take  the  condition  of  a  gravity  plant  without  storage  which 


146  PRACTICAL  IRRIGATION. 

has  sold  water  rights  up  to  the  limit  of  its  capacity,  providing 
at  certain  periods  of  the  year  its  full  capacity  will  not  be  required, 
due  to  wet  weather  or  other  causes,  no  material  saving  will 
result  to  the  company  from  this  cause,  nor  can  the  water  not 
so  used  be  disposed  of.  In  that  event  it  is  not  just  that  any- 
thing but  a  small  charge  should  be  made  for  the  same.  Broadly 
speaking,  in  a  gravity  system  the  equitable  system  of  charging 
would  tend  more  toward  a  flat-rate  system  than  toward  a  meter 
system.  The  system  proposed,  however,  is  one  which  com- 
bines the  principles  of  both  these  systems. 

In  countries  where  water  is  scarce  and  the  supply  not  equal 
to  the  demand  for  irrigation,  water  may  justly  be  assumed  to 
have  a  high  intrinsic  value  in  addition  to  the  value  of  the  right 
to  use  a  certain  flow.  This  matter  should  be  taken  into  con- 
sideration in  fixing  a  rate  per  cubic  foot  per  second.  For  a 
rate  to  be  fair  to  a  company  investing  capital  in  an  irrigation 
plant,  an  income  should  be  assured  to  the  company  in  wet  years 
as  well  as  in  dry  years,  and  any  increased  expense  for  actual 
amount  of  water  delivered  in  addition  to  the  expense  necessary 
to  be  in  position  to  deliver  a  given  flow  should  also  be  charged 
to  the  consumer  as  charge  No.  3. 


CHAPTER  XII. 
ECONOMIC    LIMIT    OF   IRRIGATION. 

THE  greater  part  of  the  present  water  supply  of  irrigation 
plants  consists  of  the  water  diverted  by  gravity  from  flowing 
streams,  conveyed  by  ditches  to  the  land.  Though  in  some 
cases  the  development  cost  of  gravity  water  so  obtained  is  high, 
still  in  the  majority  of  instances  the  cost  per  unit  volume  of 
water  diverted  is  small,  and  the  cost  of  irrigation  of  this  type 
is  particularly  low  in  comparison  with  the  greatly  increased 
productivity  of  the  land.  In  the  arid  region,  much  of  the  land 
is  of  little  or  no  value  without  water,  while  the  soil  and  climate 
are  such  that  irrigation  is  capable  of  producing  plentiful  crops 
and  proving  of  value  far  greater  than  the  cost  of  irrigation,  where 
the  development  is  not  expensive. 

According  to  Elwood  Mead:  "  If  every  drop  of  water  which 
falls  on  the  mountain  summits  could  be  utilized,  it  is  not  likely 
that  10  per  cent  of  the  total  area  of  the  arid  West  could  be  irri- 
gated, and  it  is  certain  because  of  physical  obstacles  that  it  will 
never  be  possible  to  get  water  on  even  this  small  percentage." 
The  available  proportion  of  the  rainfall  is  greatly  limited,  the 
water  being  disposed  of  in  four  manners:  Evaporation  from 
the  surface  of  the  ground,  transpiration  losses,  underground 
waters,  and  surface  run-off.  Much  of  the  water  is  lost  by 
evaporation  before  it  has  an  opportunity  to  seep  into  the  ground. 
The  preservation  of  the  forests  helps  greatly  to  diminish  this 
loss,  protecting  the  land  from  the  rays  of  the  sun,  and  allow- 
ing the  water  time  to  sink  into  the  ground,  to  join'  the  under- 
ground waters,  which  flow  through  the  subterranean  drainage 
system  of  the  country.  The  underground  supply,  which  is  the 
source  of  supply  of  all  springs  and  wells,  both  pumped  and 
artesian,  is  hence  by  no  means  unlimited  in  quantity.  It  will 
often  be  found  in  regions  where  there  has  been  very  extensive 
well-development,  that  the  static  level  of  the  water  in  the  wells 
has  greatly  lowered ;  wells  which  formerly  gave  a  strong  artesian 

147 


148  PRACTICAL   IRRIGATION. 

flow  have  weakened  in  flow  or  have  ceased  to  flow,  and  must  be 
pumped,  while  from  pumped  wells  the  water  must  be  lifted  from 
greater  depths. 

It  is  evident  that  the  actual  water  supply  which  can  be  made 
available  for  irrigation  in  the  arid  region  is  far  less  than  the 
needs  of  the  land  which  is  capable  of  being  irrigated.  As  much 
of  this  land  is  valueless  without  irrigation,  there  will  ultimately 
be  use  for  all  the  available  water  supply,  provided  the  cost  of 
development  is  not  too  great,  and  it  is  this  cost  alone  which  will 
limit  the  use  of  water.  Evidently  the  present  cost  of  irrigation 
water  will  by  no  means  determine  the  ultimate  irrigation 
development. 

Where  the  cost  of  irrigation  is  but  a  small  percentage  of  the 
benefits  derived  therefrom,  far  higher  prices  can  be  profitably 
paid  therefor. .  Water,  per  se,  has  an  intrinsic  value,  where  the 
demand  exceeds  the  supply,  quite  apart  from  the  cost  of  develop- 
ment, and  the  land  to  which  the  water  right  attaches  will  on 
that  account  increase  in  value  up  to  the  point  where  the  net 
value  of  irrigation  will  yield  a  fair  profit  on  the  increased  invest- 
ment. Hence  it  is  evident  that  irrigation  development  will 
tend  to  increase  until  the  costs  of  irrigation  will  allow  only  a 
reasonable  profit  from  its  use.  This  will  not  in  general  be 
before,  at  least  in  many  places,  the  entire  low- water  supply  is 
utilized,  and  much  of  the  water  which  now  runs  to  waste 
is  stored  in  reservoirs.  After  the  natural  flow  of  the  streams  is 
all  utilized  during  low  water,  further  development  must  come 
either  from  storing  the  surplus  water  thereof,  at  periods  when  it 
would  otherwise  run  to  waste,  or  by  developing  the  under- 
ground supply,  usually  by  the  use  of  wells.  The  development 
of  water  supply  by  these  two  methods  is  quite  extensive,  and 
although  most  wells  must  be  pumped,  still  improvements  in 
pumping  machinery  and  the  increased  use  of  electric  trans- 
mission circuits  covering  the  country  with  a  network  of  lines 
are  reducing  greatly  the  cost  of  pumping  water. 

A  study  of  present  costs  and  values  of  irrigation  brings  out 
very  forcibly  the  fact  that  a  very  extended  use  may  be  expected 
of  reservoirs  in  the  United  States,  and  that  in  many  cases  water 
may  be  stored  at  costs  well  within  the  present  actual  profitable 
costs  of  irrigation  water. 

Economic  considerations  require  that  in  the  arid  region,  with 


ECONOMIC    LIMIT    OF   IRRIGATION.  149 

its  limited  rainfall,  irrigation  development  shall  not  be  finally 
governed  by  present  cost,  but  rather  by  the  value  of  irrigation, 
and  that  this  alone  will  ultimately  determine  the  extent  of 
reservoir  construction. 

The  question  arises,  What  is  the  probable  field  for  storage 
reservoirs,  and  how  much  water  must  they  be  called  upon  to 
store?  To  answer  this  question  fully  requires  a  knowledge  of 
the  time,  value,  and  duration  of  flow  of  the  water  supply,  and 
of  the  demands  for  irrigation  water.  Also  we  must  know  the 
losses  from  the  reservoir,  and  the  periods  of  such  losses.  Reser- 
voir losses  consist  of  evaporation  and  seepage.  The  evaporation 
losses  will  in  general  vary  from  3  to  7  feet  per  year  in  arid  regions, 
and  quite  extensive  data  in  this  respect  are  available  for  various 
places  throughout  the  country,  giving  the  monthly  and  annual 
evaporation.  Seepage  losses  are  difficult  to  determine.  If  the 
bottom  of  the  reservoir  is  of  water-tight  material,  losses  of  this 
nature  will  be  small;  but  if  the  bottom  is  of  a  pervious  nature, 
it  will  be  unsuitable  for  reservoir  purposes,  and  can  be  made  to 
hold  water  only  by  lining  the  reservoir  with  impervious  material. 

According  to  Elwood  Mead,  to  utilize  the  entire  supply,  40 
per  cent  of  the  flow  of  Western  rivers  would  need  to  be  stored 
for  irrigation,  while  the  remainder  could  be  used  directly  on  the 
land  during  its  irrigation  period  of  June,  July,  August,  and 
September.  In  many  places  irrigation  is  practically  impossible 
on  any  scaje,  without  the  use  of  reservoirs,  since  the  rainfall 
may  be  so  uncertain,  and  the  drainage  area  so  rugged  and  un- 
protected, that  there  will  be  no  water  available  at  times  when  it 
is  most  needed  for  irrigation.  In  that  event  practically  all 
irrigation  water  must  be  stored. 

Artesian  wells  used  for  irrigation  in  Southern  Texas,  are 
usually  provided  with  storage  reservoirs  of  sufficient  capacity 
to  store  a  few  days'  supply  of  water.  The  irrigation  factor 
there,  which  is  the  percentage  of  the  year  during  which  the 
output  of  the  well  is  actually  used,  averaged  only  20  per  cent. 
In  other  words,  four-fifths  of  the  supply  was  not  used,  and  in  the 
majority  of  cases  went  to  waste.  This  makes  the  expense  of 
water,  which  consists  of  the  interest  on  the  cost  of,  and  of  the 
depreciation  of  the  wells,  five  times  as  great  per  unit  quantity 
of  water,  as  if  the  entire  supply  had  been  used.  If  there  had 
been  a  storage  reservoir  of  sufficient  capacity  to  have  held  the 


150  PRACTICAL  IRRIGATION. 

supply  of  water  delivered  throughout  the  year,  then  if  20  per 
cent  of  the  yearly  output  were  lost  in  evaporation  and  seepage, 
the  well  would  have  furnished  four  times  as  much  available 
water,  and  would  have  irrigated  four  times  the  area. 

If  the  fixed  charges  on  the  reservoir  were  the  same  as  on  the 
well,  then  if  the  reservoir  cost  three  times  as  much  as  the  well, 
the  cost  per  unit  of  water  would  be  the  same.  If  the  reservoir 
were  more  expensive,  then  it  would  pay  better  to  put  down  more 
wells,  provided  each  well  gave  the  same  quantity  of  water. 
This,  however,  will  not  be  the  case,  as  in  general  the  wells  will 
interfere  with  each  other  more  or  less,  and  in  some  cases  may 
give  but  little  total  increase  over  the  flow  from  only  one  well. 
The  fact  of  being  able  to  multiply  fourfold  the  available  irrigable 
area  is  no  small  argument  for  reservoir  construction. 

There  is  still  a  large  field  for  the  construction  of  reservoirs 
of  small  capacity  —  say  of  a  capacity  sufficient  to  hold  from 
twelve  hours'  to  a  week's  supply.  Many  pumping  plants 
operate  for  only  12  hours  per  day,  as  night  irrigation  is  not 
generally  desirable.  This  results  in  having  to  install  plants 
far  larger  than  would  otherwise  be  necessary.  In  Southern 
Texas  the  irrigation  factor  of  the  pumping  plants  was  only  14 
per  cent.  In  other  words,  on  the  average  the  plants  ran  only 
one-seventh  of  the  time.  The  total  fixed  expenses  of  the  plants, 
consisting  of  interest  and  depreciation,  were  about  equal  to  the 
sum  of  the  labor  and  fuel  expenses,  while  in  the  average  case  the 
fixed  expenses  were  about  three  times  the  sum  of  the  average 
labor  and  fuel  expenses.  The  labor  expense  was  a  compara- 
tively small  item.  Many  of  the  plants  operated  only  12  hours 
a  day,  thus  necessitating  a  greatly  increased  first  cost  of  plant 
over  what  would  be  necessary  with  the  use  of  a  reservoir  and  a 
smaller  plant,  for  as  labor  is  so  cheap,  the  cost  of  pumping  would 
be  much  reduced,  and  the  initial  investment  also,  by  operating 
the  plant  continuously  night  and  day,  storing  the  water  pumped 
at  night,  in  a  reservoir. 

The  advantages  of  small  reservoirs  are  numerous  and  have 
already  been  discussed  (see  p.  48).  Suffice  it  to  say,  that 
many  very  small  pumping  plants,  realizing  the  advantage  to  be 
derived,  have  constructed  reservoirs  to  aid  in  the  operation  of 
the  plants. 

To  give  some  idea  of  the  present  cost  of  irrigation  water,  the 


ECONOMIC    LIMIT   OF   IRRIGATION.  151 

average  cost  of  pumped  water  in  Southern  Texas  in  1904,  using 
straight  averages  was  $12  per  acre-foot,  and  the  average  cost 
per  acre  irrigated  was  $16  to  $20,  while  the  cost  of  irrigation, 
using  the  weighted  averages,  was  from  $5  for  steam  plants  under 
low  lifts,  to  $18  for  gasoline  plants,  per  acre,  per  year,  the 
average  being  $6  for  all  plants  and  $12  for  plants  not  used  for 
rice  irrigation.  As  the  average  depth  for  gasoline  plants  was  1.0 
foot,  the  maximum  average  cost  of  water  was  $18  per  acre-foot. 
The  highest  price  paid  for  water  for  irrigation  in  Southern  Texas 
was  $50  per  acre-foot.  This  water  was  delivered  from  a  pipe  line. 
This  cost,  it  is  true,  is  excessive  for  anything  except  truck  irri- 
gation. One  thing  particularly  noticeable  about  irrigation  is  that 
the  depth  of  water  used  varies  inversely  with  the  cost,  and  that 
high  cost  tends  to  economical  use  of  water.  If  the  same  quantity 
of  water  were  to  be  used  when  water  is  dear,  as  is  used  when  it 
is  cheap,  the  irrigation  would  be  impracticable.  However, 
by  more  careful  distribution  and  use,  the  farmer  finds  he  can 
get  along  with  a  far  smaller  quantity  of  water,  and  the  high 
cost  is  no  longer  prohibitive. 

The  depth  of  irrigation  water  varies  largely  with  the  crop, 
soil,  climate,  and  cost,  not  to  mention  the  irrigator  himself. 
In  arid  climates  the  depth  usually  applied  is  2  to  5  feet. 
Where  the  water  is  distributed  with  care,  a  depth  of  2  feet 
will  often  provide  sufficient  irrigation  unless  conditions  are 
unfavorable.  In  semi-arid  climates  wrhere  the  water  is  skillfully 
used,  and  the  soil  suitable,  frequently  not  over  1  foot  of  irriga- 
tion water  is  employed  per  year;  and  often  great  benefits  are 
derived  from  6  inches,  judiciously  used.  In  some  sections  as 
much  as  10  feet  are  used  per  year,  but  this  is  excessive. 

The  value  of  irrigation  depends  on  the  crops,  the  seasons, 
and  the  distance  to  market.  For  truck,  it  is  not  uncommon  for 
irrigation  to  be  worth  from  $100  to  $300  per  acre,  and  in  some 
cases  as  high  as  $1500.  The  total  value  of  field  crops  will  vary 
from  $20  to  $80  per  acre,  and  irrigation  will  be  worth,  for  such 
purposes,  up  to  as  high  as  $50  per  acre.  These  figures  have 
been  given  in  order  to  furnish  some  idea  of  the  values  and  costs 
of  irrigation,  and  to  have  a  standpoint,  somewhat  indefinite 
it  may  be  said,  from  which  to  view  the  possibilities  of  storage 
of  water  for  irrigation.  The  problem  is  quite  complex  from  the 
number  of  variables  which  must  enter  into  it.  Each  case 


152  PRACTICAL  IRRIGATION. 

should  be  figured  out  for  itself,  as  it  is  absolutely  impossible  to 
lay  down  figures  for  general  guidance. 

Great  economic  advantages  may  be  derived  from  the  use  of 
reservoirs  and  storage  tanks,  both  large  and  small;  and,  as  will 
be  shown,  they  may  be  made  effective,  not  alone  in  increasing 
the  available  irrigable  area,  but  also  by  diminishing  largely  the 
first  cost  and  operating  expenses  of  lands  irrigated  by  pumping 
plants  and  artesian  wells,  as  well  as  by  gravity  systems.  Inves- 
tigations show  that  where  the  ground  is  at  all  suitable,  large 
reservoirs  may  be  constructed  entirely  in  embankment,  on 
level  or  gently  sloping  ground,  at  a  less  cost  than  the  average 
cost  of  construction  of  natural  reservoirs  now  built.  There 
are  many  places  in  the  country  whefe  such  reservoirs  can  be 
constructed,  where  no  natural  site  now  exists.  This  is  most 
significant,  when  it  is  fully  understood.  Water  may  even  be 
pumped  to  considerable  elevation,  and  stored  in  reservoirs  con- 
structed in  embankment,  and  supplied  therefrom  at  prices  com- 
parable with  present  costs  of  pumping  alone,  so  that  places 
without  present  irrigation  facilities  may  come  under  its  bene- 
ficial influence.  There  are  many  elements  entering  into  the 
economic  construction  of  reservoirs  of  this  nature,  but  if  all 
necessary  data  are  given,  the  design  of  the  reservoir  can  be 
figured  mathematically  to  deliver  a  given  quantity  of  water  at 
as  cheap  a  cost  as  possible.  Engineers  may  differ  as  to  the 
probable  values  to  be  assigned  to  the  various  costs,  but  the 
principles  of  determination  of  dimensions  remain  the  same. 
In  any  given  case  it  would  doubtless  be  possible,  if  the  reservoir 
be  large,  to  have  a  site  possessing  some  natural  advantages, 
even  on  comparatively  level  ground.  The  figures  given  for 
large  reservoirs,  and  the  method  employed,  will  probably  be 
useful,  not  so  much  in  an  individual  case,  owing  to  the  variation 
of  conditions  encountered,  as  to  direct  attention  to  the  feasibility, 
or  lack  of  feasibility,  of  such  undertakings,  and  to  suggest 
alternative  plans  for  irrigation  and  reservoir  projects.  It  is 
particularly  necessary  to  verify,  as  far  as  possible,  the  assump- 
tions for  any  actual  case,  and  to  note  the  effect  of  changes  in  the 
assumptions  which  might  be  liable  to  occur. 


CHAPTER  XIII. 
EARTH  TANKS. 

THE  small  earth  tank  has  an  important  position  in  many 
kinds  of  irrigation  on  a  small  scale,  where  the  supply  is  of 
limited  capacity.  It  is,  however,  not  uncommon  to  see  tanks 
constructed  at  a  cost  fully  twice  as  great  as  should  be  the 
case. 

The  section  of  a  reservoir  to  be  adopted  depends  in  part  on  the 
land  which  it  is  desired  to  allot  to  it,  but  it  should  be  remembered 
that  the  circle  has  a  larger  area  for  a  given  perimeter  than  any 
other  figure,  and  hence  on  level  ground  circular  reservoirs  will 
contain  considerably  less  material  in  the  banks  for  a  given 
capacity.  Thus  a  square  tank  will  have  13  per  cent  more  material 
in  its  banks  than  a  circular  tank  of  the  same  capacity,  and  hence 
will  cost  13  per  cent  more.  With  a  rectangular  tank  the  expense 
will  be  increased  to  considerably  greater  extent.  Thus,  for 
example,  a  rectangular  tank  twice  as  long  as  it  is  wide,  and  of 
the  same  area  as  a  square  tank,  will  have  a  perimeter  6  per  cent 
greater  than  the  equivalent  square,  and  20  per  cent  greater 
than  the  equivalent  circle.  If  the  rectangular  tank  be  of  three 
times  greater  length  than  its  width,  it  would  have  a  perimeter 
15  per  cent  greater  than  the  equivalent  square,  and  31  per  cent 
greater  than  the  equivalent  circle,  though  the  increased  volume 
of  the  banks  may  not  be  quite  as  great  as  these  figures  would 
show.  In  considering  the  reservoir  problem,  all  reservoirs  will 
be  assumed  to  be  of  circular  section  unless  specifically  stated  to 
the  contrary.  All  linear  dimensions  will  be  in  feet,  and  cubical 
contents  of  the  reservoir  banks  will  be  in  cubic  yards;  reservoir 
capacities  will  be  in  acre-feet. 

The  common  method  in  use  in  figuring  reservoir  capacity  of 
small  earth  tanks  is  to  figure  the  entire  capacity  from  the  bottom 
of  the  reservoir  to  the  top  of  the  bank.  This  method  is  both 
misleading  and  erroneous,  since  without  pumping  from  the 

153 


154 


PRACTICAL  IRRIGATION. 


reservoirs,  the  water  cannot  be  drawn  below  the  level  of  the 
ground,  and  the  reservoir  should  not  be  filled  level  with  the  top 
of  the  banks,  but  a  safe  margin  must  be  left  to  provide  for 
wave  action.  This  margin,  which  is  the  vertical  distance 
between  the  top  of  the  bank  and  the  highest  safe  water  level  in 
the  reservoir,  we  shall  call  clearance.  It  should  depend  largely 
on  the  size  of  the  reservoir,  and,  unless  specified  to  the  contrary, 


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Fig.  30.     Reservoir  Clearance. 

it  will  be  defined  by  the  equation,  b  =  clearance  =  0.06 
(10  +  \/d)  feet,  up  to  a  clearance  of  3  feet,  after  which  it  will 
remain  constant  for  larger  diameters.  In  this  equation  d  = 
inside  base  diameter  of  the  reservoir  in  feet.  The  relation 
between  clearance  and  inside  base  diameter  is  graphically 
represented  in  the  curve  in  Fig.  30.  Thus,  for  example,  to  find 
the  clearance  for  a  reservoir  of  900  feet  inside  base  diameter, 


-outside  6ase  afi'a. 


Fig.  31.     Reservoir  Capacity  Diagram. 

follow  the  vertical  line  representing  900  feet  up  to  the  point 
where  it  strikes  the  curve.  The  corresponding  vertical  distance 
as  measured  by  the  vertical  height  of  this  line  is  2.4  feet. 
The  proper  clearance  depends  on  the  exposure  of  the  reservoir 
to  winds,  and  on  the  probable  intensity  of  the  winds.  The 
actual  capacity  of  the  reservoir  we  shall  figure  as  that  capacity 
which  is  included  between  the  elevation  of  the  lowest  original 
ground  level  in  the  reservoir  and  that  of  the  highest  safe  water 
level,  defined  by  allowing  for  the  clearance,  as  above  (see  Fig.  31). 


EARTH    TANKS.  155 

Stevenson's  formula  for  the  relation  between  the  wave  height, 
H  ft.,  due  to  wind  and  jthe  fetch,  F,  nautical  miles,  is  as  follows: 

H  =  1.5  VF  +  2.5^F  _or  expressing  the  fetch  in  feet  D. 
H  =  .0191  VD  +  .281  ^D. 

The  formula  gives  the  following  results: 

D  =      100  H  =  1.08 

400 1.64 

900  2.11 

1600 2.53 

2500 2.94 

5000 3.71 

10000 4.72 

20000 6.02 

Throughout  the  remainder  of  this  discussion  three  general 
cases  will  be  considered  in  reservoir  construction: 

Case  1.  —  Where  the  reservoir  banks  are  built  on  a  slope  of 
3  horizontal  to  1  vertical  on  the  inside,  and  2  to  1  on  the  outside. 

Case  2. — Where  the  slope  of  the  bank  is  2  to  1  on  the  inside, 
and  1.5  to  1  on  the  outside. 

Case  3.  —  Where  the  reservoir  is  lined,  inside  and  outside 
slopes  being  1.5  to  1.  The  reservoirs  will  be  considered  to  be 
constructed  on  level  ground,  and  no  allowance  will  be  made  in 
the  capacity  of  the  reservoir  for  dirt  which  may  be  excavated 
from  banks  below  the  level  of  the  ground,  the  lowest  plane  to 
which  the  water  may  be  drawn  in  the  reservoir  being  con- 
sidered as  that  of  the  ground  level.  The  following  notation  will 
be  adopted,  linear  dimensions  being  in  feet: 

H  =  vertical  depth  of  reservoir  bank. 

S  =  1  divided  by  inside  slope  of  reservoir. 

P  =  1  divided  by  outside  slope  of  reservoir. 
W  =  crown  of  reservoir  bank. 
Y  =  cubic  yards  of  earth  in  the  reservoir. 
r    =  radius  of  inside  base  of  reservoir. 
r'    =  radius  of  reservoir  at  the  top  of  the  water  line. 

InCasel,S  =  3  P  =  2. 
In  Case  2,  S  =  2  P  =  1.5. 
In  Case  3,  S  =-  P  =  1.5. 


156  PRACTICAL  IRRIGATION. 

On  page  219  in  the  Appendix  is  given  the  method  of  calcu- 
lation of  reservoir  capacities,  and  of  the  volumes  of  earth  in 
embankments. 

Capacity  of  reservoir  in  Case  1  =  (r/3- r3)  X  (0.00000801)  - 
acre-feet,  and  the  flow  in  gallons  per  minute  required  to  fill  the 
reservoir  in  24  hours  is  (r'3  -  r3)  X  0.00181. 

For  Case  2,  acre-feet  capacity  of  reservoir  equals  0.00001201 
(r'3  —  r3),  and  gallons  per  minute  required  to  fill  reservoir  in 
24  hours  =  (r'3  -  r3)  .002715. 

In  Case  3,  acre-feet  capacity  equals  0.00001602  (r*  -  r3),  and 
the  gallons  per  minute  required  to  fill  the  reservoir  in  24  hours  = 
(ri»  _  rs)  0.00362. 

As  the  use  of  small  reservoirs  in  irrigation  work  is  quite 
extended,  several  tables  have  been  prepared  to  aid  in  the  com- 
putation of  capacities  of  reservoirs  and  the  volumes  of  earth 
in  the  embankments  of  the  same.  Two  units  of  capacity  are 
used  —  the  acre-foot  of  water,  and  the  flow  in  gallons  per 
minute  required  to  fill  the  reservoir  in  24  hours.  Reservoir 
capacity  is  often  conveniently  expressed  in  the  hours  or  days 
required  for  the  rate  of  supply  to  fill  the  tank.  For  instance, 
say  the  reservoir  is  required  to  hold  5  days'  continuous  supply 
of  a  pump  delivering  40  gallons  per  minute.  This  is  equivalent 
to  200  gallons  per  minute  for  one  day.  Looking  in  Table  VIII, 
the  required  capacity  is  0.88  acre-foot.  Any  diameter  of  reser- 
voir may  be  assumed  from  which  the  corresponding  depth  of 
water  may  be  calculated  for  a  given  capacity.  Then  allowing  for 
a  safe  distance  between  the  top  of  the  water  and  the  top  of  the 
bank,  the  volume  of  bank  may  be  figured.  In  general  it  will 
appear  that  there  will  be  greatly  different  volumes  of  earth  in 
the  banks  for  the  different  depths  of  water  for  reservoirs  of 
the  same  capacity.  It  is  to  avoid  figuring  these  quantities  that 
the  tables  and  curves  referred  to  have  been  given. 

Table  LXVIII  gives  capacities  of  various  cone  reservoirs  for 
each  foot  in  depth.  (See  p.  205.) 

Table  LXIX  gives  data  with  reference  to  the  circular  reser- 
voirs for  Case  1.  (See  page  209.) 

Table  LXX  gives  corresponding  data  with  Case  2.    (See  p.  212.) 

The  capacities  in  Tables  LXIX  and  LXX  are  calculated 
on  the  assumption  that  the  reservoir  is  filled  to  the  top  of  the 
bank  and  has  no  clearance.  Column  1  gives  inside  base  diameter 


EARTH    TANKS. 


157 


(2  r)  of  the  reservoir.  Column  2  gives  vertical  depth  of  reservoir 
( H) .  Column  3  gives  top  inside  diameter  of  reservoir.  Column 
4  gives  capacity  of  reservoir  in  acre-feet  when  filled  level  with  the 
top.  Column  5  gives  flow  in  gallons  per  minute  necessary  to  fill 


250 


5C 


-Mjoatity  in  acre-ft 
Fig.  32.     Reservoir  Capacities  for  Different  Water  Depths.     Case  1. 

the  reservoir  in  24  hours.  Columns  6,  7,  and  8  give  cubic 
yards  of  earth  in  embankment,  with  crowns  of  3,  4,  and  5  feet 
respectively.  Column  9  gives  outside  base  diameter  of  reservoir 
with  4-foot  crown.  Column  10  gives  length  of  side  of  inside 


§» 

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20C 


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cafxtcifi/  z/?   acre -ft. 


Fig.  33.    Reservoir  Capacities  for  Different  Water  Depths.    Cose  1. 

base  of  equivalent  square  reservoir.  Column  11  gives  length 
of  side  of  top  inside  of  equivalent  square  reservoir.  Column  12 
gives  length  of  base  outside  of  equivalent  square  reservoir,  with 
4-foot  crown.  Figs.  32  and  33  represent  graphically  the  capaci- 


158 


PRACTICAL  IRRIGATION. 


ties  in  acre-feet  of  reservoirs  of  various  base  inside  diameters  and 
depths  of  water.  Each  curve  in  these  figures,  which  represent 
part  of  Table  LXIX,  Case  1,  is  drawn  for  a  given  depth  of 
water  in  the  reservoir,  and  represents  the  relation  existing 


250 


jf  5  V 

capacity  7/7  acre-fl 
Fig.  34.     Reservoir  Capacities  for  Different  Water  Depths.     Case  2. 

between  the  inside  base  diameter  and  the  capacity  of  the 
reservoir  in  acre-feet.  As  an  example  of  the  use  of  these  curves, 
suppose  that  it  was  desired  to  build  a  reservoir  with  a  capacity 
of  2.5  acre-feet  with  a  depth  of  5  feet  of  water.  Looking  along 


* 

I 

Wtf 


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200 


// 


M- 


W 


z~z 


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so 


capacity  in    acre-ft' 

Fig.  35.     Reservoir  Capacities  for  Different  Water  Depths.     Case  2. 

the  vertical  line  representing  2.5  acre-feet  in  capacity,  note  the 
point  at  which  it  crosses  the  curved  line  representing  a  reservoir 
5  feet  in  depth.  The  corresponding  inside  base  diameter  of  the 
reservoir  is  151  feet.  Should  it  be  desired  to  build  this  reservoir 


EARTH    TANKS. 


159 


to  the  water  depth  of  4  feet,  similarly  the  inside  base  diameter 
of  the  reservoir  would  be  175  feet.  Figs.  34  and  35  show  similar 
curves  for  Case  2. 

Figs.  36  and  37  represent  graphically  the  relation  existing 


eso 


00^          ,,3000 . 5000  QOOQ. 

qr  earc/i  (n  emoanxmefJi 

Fig.  36.    Capacities  and  Volumes  of  Embankment.     Case   1. 

between  the  inside  base  diameter  and  the  cubic  yards  of  earth 
in  the  embankment  in  the  circular  reservoir  for  Case  1,  the  crown 
being  4  feet.  The  straight  lines  running  diagonally  across  the 
sheet  represent  the  relation  existing  between  the  inside  base 


eoo 


-      egop  .         i/ooo        .  /woo 

.  of  eart/i    in   embankment 

Fig.  37.    Capacities  and  Volumes  of  Embankment.     Case  1. 

diameter  and  the  cubic  yards  of  earth  in  the  reservoir  embank- 
ment for  various  depths  of  embankment.  Thus,  for  example, 
if  it  were  desired  to  tell  the  cubic  yards  of  earth  in  the  em- 
bankment of  a  reservoir  500  feet  inside  base  diameter  and  5  feet 


160 


PRACTICAL  IRRIGATION. 


deep,  follow  the  diagonal  line  representing  5  feet  in  depth  until 
it  crosses  the  horizontal  line  marked  500.  The  horizontal  dis- 
tance of  this  line  from  the  zero  vertical  line  represents  the 


£00 


\TTVI7 


O  500  1000  1500      ,    2OOQ,    '  „     SfOQ       ,     3OOQ  <3$00 ¥OOO 

cu,^icf.  <f  earth  in  emoannmenf 

Fig.  38.     Capacities  and  Volumes  of  Embankment.     Case  2. 

cubic  yards  of  earth  in  the  embankment  of  the  reservoir 
which,  in  this  case,  is  5150.  At  10  cents  per  cubic  yard, 
this  would  cost  $515  for  the  construction.  On  the  same 


XJ5BO 

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?               JOOO            ZOOO           JOOO           .¥OOQ            SOO&             6OOO            7OOO           &X, 
cu.j/ct.  of  earth   in  emSankment 

Fig.  39.    Capacities  and  Volumes  of  Embankment.     Case  2. 

sheets  are  drawn  curved  lines  which  represent  the  relations 
existing  between  the  inside  base  diameter,  depth  of  reservoir, 
and  cubic  yards  of  earth  in  embankment.  These  lines  are 
drawn  for  various  capacities  of  reservoirs,  the  assumed  clearance 


EARTH    TANKS. 


161 


being  allowed  for  in  the  figures.  Thus,  for  example,  suppose 
it  is  desired  to  construct  a  reservoir  to  hold  10  acre-feet  of  water. 
Follow  along  the  curved  line  marked  10  acre-feet;  note  the  point 


acre  -ft.  capacity 
Fig.  40.    Minimum  Volumes  of  Embankments  for  Different  Capacities. 

of  intersection  of  this  curved  line  with  the  straight  diagonal 
line.   The  horizontal  distance  to  such  point  of  intersection  from 


S50 


I  50 


acre -ft.  capacity 

Fig.  41.    Minimum  Volumes  of  Embankments  for  Different  Capacities. 

the  zero  line  represents  cubic  yards  of  earth  in  embankment, 
whereas  the  vertical  distance  above  the  zero  line  represents 
inside  base  diameter  in  feet.  Thus  it  will  be  seen  that  the 


162 


PRACTICAL  IRRIGATION. 


1 


reservoir  may  be  constructed  with  banks  4  feet  deep,  with  an 
inside  base  diameter  of  520  feet,  with  3600  cubic  yards  of  earth, 
or  it  may  be  constructed  with  banks  5  feet  deep,  405  feet  inside 

base  diameter,  with 
4200  yards  of  earth, 
or  6  feet  deep,  346 
feet  inside  base  dia- 
meter, with  5200 
cubic  yards  of  earth, 
and  so  on.  Figs. 
38  and  39  represent 
similar  curves  for 
Case  2.  Table 
LXXII,p.216,gives 
coefficients  for  de- 
termining the  vol- 
ume of  earth  in 
circular  reservoir 
embankments. 

Figs.  40  and  41, 
Tables  LXXIII  and 
LXXIV,  pp.  217 
and  218,  give  the 
dimensions  of  reser- 
voirs of  various  ca- 
pacities constructed 
with  a  minimum 
amount  of  earth  in 
the  embankment  to 
attain  that  capacity 
for  Cases  1  and  2. 
They  indicate  also 
the  relation  between 
the  capacity,  volume 


1 


of  earth  in  embank- 
ment, and  volume  of 
earth  per  acre-foot  of 
capacity.  They  are  calculated  according  to  the  laws  of  clearance 
specified  in  the  tables.  To  illustrate  the  use  of  the  tables,  assume 
that  it  is  desired  to  construct  a  reservoir  of  31  acre-feet  capacity, 


EARTH    TANKS. 


163 


Case  1.  What  is  the  minimum  amount  of  material  which  can 
be  used  in  the  reservoir  embankment,  and  what  must  be  the 
corresponding  inside  base  diameter  and  depth  of  the  reservoir? 
Taking  the  vertical  line  marked  31  in  Fig.  40,  note  the  point 


where  this  crosses  the  curve  1,  which  is  at  a  vertical  distance 
235  on  the  scale  above  zero,  thus  indicating  that  235  cubic 
yards  of  earth  are  required  for  1  acre-foot  of  capacity.  Hence 
the  reservoir  embankment  requires  7300  cubic  yards  of  earth. 
From  Table  LXXIII  it  will  be  seen  that  this  would  call  for  an 


164 


PRACTICAL  IRRIGATION. 


inside  base  diameter  of  1000  feet  and  depth  of  embankment 
of  4.2  feet.    Also  that  the  depth  of  water  would  be  1.7  feet. 

A  study  of  these  curves  indicates  that  for  a  reservoir  of  given 
capacity  the  depth  should  be  relatively  exceedingly  small  in 
order  to  construct  it  as  cheaply  as  possible,  the  expense  of  con- 
struction being  figured  at  merely  a  given  rate  per  cubic  yard 
of  material  in  the  embankment.  Practical  consideration  of  the 


JOOOG 


1000 


IOOOOO  2OOQOO  .  3OOOOO 

cu.j/ct.   of  earth    in     e?T?6a.r?ti7r>ent 

Fig.  44.    Capacities  and  Volumes  of  Embankments.     Case  2. 


use  to  which  the  reservoir  is  to  be  put  will  largely  modify  the 
best  proportions  of  diameter  and  base  for  a  given  capacity, 
the  proper  dimensions  being  arrived  at  only  after  thorough  con- 
siderations of  all  the  various  features  of  the  case.  For  example, 
evaporation  from  reservoirs  will  preclude  the  use  of  shallow 
construction,  provided  the  water  must  be  retained  in  the  reser- 
voir for  a  considerable  period  of  time.  The  value  of  the  land 
also  necessitates  economy  in  the  area  occupied  by  the  reservoir, 
and  calls  for  deeper  reservoirs  than  would  otherwise  be  advisable. 


/•:.!/,'  777     TAXKS.  165 

Where  the  clearance  is  3  feet  and  is  taken  as  a  constant  the  most 
economical  depth  of  water  in  the  reservoir  is  1.23  feet  in  Case  1, 
and  1.3  feet  in  Case  2. 

A  study  of  the  curves  of  Figs.  36  to  39,  however,  indicates  that 
considerable  variation  may  be  made  in  the  depth  of  reservoirs  of 
given  capacity  without  affecting  to  any  great  extent  the  total 
volume  of  earth  in  the  embankment.  The  table  of  minimum 
volumes  of  earth  is  chiefly  useful  as  a  guide  in  determining  the 
relative  cost  of  reservoirs  of  given  capacity.  Table  LXXI,  page 
215,  and  Fig.  42  indicate  the  relation  existing  between  the 
capacity  in  acre-feet  and  the  depth  of  water  in  large  circular 
reservoirs  in  Case  1.  The  values  in  Case  2  are  very  nearly  the 
same  for  reservoirs  of  such  large  capacity. 

Fig.  43  represents  the  relation  between  diameter  volumes  of 
embankment,  depth,  and  capacities  of  large  reservoirs,  Case  1 
allowing  for  clearance  of  3  feet,  and  Fig.  44  represents  corre- 
sponding relations  for  Case  2. 


CHAPTER  XIV. 
LARGE  ARTIFICIAL  RESERVOIRS. 

THERE  are  many  localities  in  the  country  where  for  part  of  the 
year  large  amounts  of  water  go  to  waste.  Where  no  natural 
reservoir  site  is  obtainable,  often  no  practical  consideration 
has  been  devoted  to  the  idea  of  the  construction  of  large  reser- 
voirs on  level  ground  for  the  storage  of  this  water  for  irrigation. 
A  study  of  the  problem  of  construction  of  earth  reservoirs  on 
level  ground  brings  out  the  fact  that  where  the  ground  is  suit- 
able for  reservoir  construction  extensive  developments  can  be 
made  along  lines  of  this  nature.  It  brings  out,  however,  most 
prominently  the  importance,  from  a  financial  standpoint,  of 
undertaking  on  a  large  scale  the  construction  of  extensive 
reservoirs.  While  it  is  true  that  large  areas,  miles  in  extent, 
cannot  usually  be  obtained  on  level  ground,  still  the  cost  of 
construction  with  a  moderate  slope  is  little  in  excess  of  the  cost 
on  level  ground.  And  the  figures  of  reservoir  construction  here- 
with presented  indicate  that  it  is  well  worth  considering  and 
investigating  thoroughly  the  problem  of  the  construction  of 
almost  the  entire  reservoir  embankment,  utilizing  at  the  same 
time  whatever  natural  advantages  may  be  found  in  the  location 
of  the  site.  In  problems  of  this  nature  it  is  particularly  important 
to  figure  carefully  all  the  various  items  affecting  reservoir  con- 
struction, probable  supply  of  water,  and  season  thereof,  evapo- 
ration, seepage,  and  the  needs  of  the  land  for  irrigation.  Also 
cost  of  construction  of  embankment  and  of  riprap.  Upon  mak- 
ing the  necessary  assumptions  of  these  quantities,  mathematical 
expressions  can  be  derived  from  which  it  is  possible  to  determine 
the  proportions  of  the  reservoir  which  will  give  a  minimum 
annual  cost  for  any  given  number  of  acre-feet  output  of 
reservoir. 

The  following  notation  will  be  used  for  reservoir  calculations, 
all  linear  dimensions  being  in  feet,  and  all  costs  in  dollars. 

166 


1. .\ /:<,!•:   ARTIFICIAL   ///•>/•;  WO/flS.  167 

A  =  acre-feet  capacity  annually  available  for  irrigation  after 
allowing  for  seepage  and  evaporation. 

B+b  +  g-k. 

C=b+g  +  d-c-k. 

D  =  total  annual  cost  =  interest  on  and  depreciation  and  main- 
tenance of  reservoir  +  cost  of  water  supplied  to  the  same. 

E  =  -    =  cost  per  acre-foot  of  water  supplied  from  reservoir. 

H  =  Depth  of  bank. 
1 


p  = 


slope  of  outside  bank 
slope  of  inside  bank 

r      (P  +  S) 

2 

R  =ioo  ' 

W '  =  crown  of  bank. 

6  =  clearance. 

c  =  depth  in  reservoir  of  annual  evaporation  and  seepage. 

d  =  annual  rainfall. 

g  =  depth  in  reservoir  of  evaporation  +  seepage  loss  during 

the  irrigation  season, 
i  =  annual  rate  of  interest. 
k  =  depth  of  water  supplied  to  the  reservoir  during  irrigation 

season. 

I  =  cost  per  acre-foot   of   water  delivered  to  the  reservoir, 
m  =  cost  of  riprap  per  square  foot. 

n  =  cost  of  construction  of  embankment  per  cubic  yard. 
p  =  per  cent  annual  interest  and  depreciation  and  mainte- 
nance of  the  reservoir  complete. 
r  =  inside  radius  of  reservoir. 
v  =  cost  of  land  per  acre. 
q  =  an  assumed  constant. 

Width  of  belt  of  riprap  =  S(H  -  q),  will  be  assumed  in  some 
cases. 

The  annual   depth  of  water  output  from  the  reservoir  =  H 
-b-n  +  jc=H-B. 


168  PRACTICAL  IRRIGATION. 

Annual  depth  of  water  which  must  be  supplied  from  sources 
other  than  rainfall  to  the  reservoir  =  H  —  b  —  d  —  g  +  c  +  k 
=  H  -C. 

It  is  assumed  that  there  is  no  rainfall  during  the  irrigation 
season.  In  the  appendix,  page  220,  is  given  in  detail  a  mathe- 
matical treatment  of  the  method  of  obtaining  the  most  economical 
proportions  of  the  reservoir  for  minimum  annual  cost  per  acre- 
foot  output.  In  the  consideration  of  the  problem  it  may  be 
stated  as  a  general  rule  that  evaporation  losses  will  be  greatest 
during  the  irrigation  season,  also  during  this  time  there  will  be, 
in  all  probability,  periods  when  a  limited  amount  of  water  can 
be  supplied  to  the  reservoir  from  the  source  of  supply,  though 
the  amount  which  can  be  furnished  at  such  time  may  be  materi- 
ally less  than  that  which  can  be  supplied  during  the  remainder 
of  the  year.  To  illustrate  the  results  of  the  application  of  the 
methods  of  reservoir  designs  cited,  the  following  assumptions 
will  be  made: 

W  =  4;  b  =  3;  c  =  6;  d  =  2;  g  =  4;  p  =  0.10;  i  =  0.07; 
k  =  1;  q  =  5;  hence,  B  =  6;  C  =  2. 

These  assumptions  mean  that  the  annual  evaporation  and 
seepage  is  6  feet.  The  evaporation  and  seepage  during  the  irri- 
gation season  is  4  feet;  the  annual  rainfall  2  feet,  and  the  depth 
of  water  supplied  to  the  reservoir  from  the  source  of  supply 
during  the  irrigation  season,  1  foot,  no  rainfall  being  supposed 
to  furnish  water  during  that  period.  The  following  additional 
assumptions  will  be  made: 

Cost  of  earthwork  =  10  cents  per  cu.  yd.,  which  will  hold 
for  short  hauls  and  where  labor  is  cheap.  The  cost  of  riprap  = 
27  cents  per  sq.  yd.,  or  n  =  0.1  ;m  =  0.03.  Under  these 
assumptions  the  following  four  cases  will  be  considered. 

Case  1-a.  —  I  =  $0.25  =  cost  per  acre-foot  of  water  furnished 
to  reservoirs;  v  =  $5  =  cost  per  acre  of  land;  S  =  3;  P  =  2; 
T  =  2.5  feet. 

Case  2-a.— The  assumptions  I  =  $0.25;  v  =  $5;  S  =  2;  P  = 
1.5  feet;  T  =  1.75. 

Case  1-b.  —  I  =  $2;   v  =  $30;   S  =  3;    P  =  2;    T  =  2.5. 

Case  2-b.  —  I  =  $2;  v  =  $30;  S  =  2;  P  =  1.5;  T  =  2.5. 

Several  other  cases  of  reservoir  construction  will  be  calculated, 
the  assumed  data  being  given  in  Table  LXVII,  p.  203. 


LARGE   ARTIFICIAL   RESERVOIRS.  169 

Tables  XXXIV,  XXXV,  XXXIX  and  XL  and  curves  in  Figs. 
l.~>,  -\(\,  47  and  4S  show  the  result  of  these  calculations.  There 
are  many  places  in  the  country  where  all  expenses  for  pumping 
water  up  to  a  head  as  high  as  80  feet  should  be  covered  by  a 
charge  of  $2  per  acre-foot,  provided  that  stations  with  an  out- 
put of  about  10  cubic  feet  per  second  be  operated  for  about 
half  the  time.  A  cost  of  $30  per  acre  for  land  is  sufficient  to 
cover  most  cases  to  be  considered,  so  the  conditions  of  Case  b 
may  be  assumed  to  represent  an  extreme  case  covering  the  cost 
of  pumping  water  into  a  reservoir  where  the  supply  is  abundant 
about  half  the  year,  mainly  when  not  needed  for  irrigation. 
\Yliile  the  results  given  in  the  tables,  and  the  curves  represent 
the  best  proportions  of  the  reservoir,  still,  should  local  con- 
ditions demand  for  any  reason,  such  as  the  lay  of  the  land,  the 
relative  dimensions  of  reservoir  may  be  altered  quite  widely 
without  materially  increasing  the  annual  cost  of  water.  The 
curves  shown  in  Figs.  45  to  48  are  of  four  kinds.  Curve  No.  1 
represents  the  relation  between  the  inside  diameter  of  the 
reservoir  and  the  output  capacity  in  acre-feet.  Curve  No.  2 
represents  the  relation  between  the  inside  diameter  and  the 
depth  of  embankment.  Curve  No.  3  represents  the  relation 
between  the  inside  base  diameter  and  the  cost  of  construction 
of  reservoir  and  riprap  per  acre-foot  output  capacity,  and  curve 
No.  4  represents  the  relation  between  the  inside  diameter  and 
the  annual  cost  per  acre-foot  output  of  reservoir.  For  example, 
if  it  were  desired  to  have  a  reservoir  delivering  1380  acre-feet  of 
water  per  year,  in  Case  1-&,  follow  out  the  horizontal  line  marked 
1380  acre-feet  to  a  point  where  it  crosses  Curve  No.  1,  the  point 
of  intersection  will  be  at  a  horizontal  distance  representing  3000 
feet.  Follow  this  vertical  line  to  a  point  where  it  crosses  Curve 
No.  4.  The  vertical  distance  of  this  point  from  the  zero  line 
shows  that  the  cost  of  water  is  $5.25  per  acre-foot.  This  is  less 
than  one-third  the  actual  cost  in  many  localities  where  irrigation 
has  been  successfully  carried  on.  To  compare  this  with  other 
costs,  the  cost  of  distribution  of  this  water  to  various  farms  should 
be  added.  In  certain  localities,  where  the  water  supply  is  lim- 
ited, the  average  cost  of  gasoline  alone  for  pumping  is  $13  per 
acre-foot.  Water  supplied  from  city  pipe  lines  costs  from  $48 
t<>  s»iO  per  acre-foot.  The  amount  of  water  needed  for  the  irri- 
gation of  land  depends  largely  on  the  method  of  distribution. 


tooo 


2$0 


20<%  20000 


so^sooo 


¥000  6OOQ  80QO   .       _./ 

inside  diet,  of  reservoir  in  ft. 


/WOO 


Fig.  45.    Economic  Reservoir  Dimensions  and  Costs.    Case  la. 


WOO.         , .  6OOQ  BOQO  .     M 

inside  <2ia.  <y   reservoir  //?  ft. 

Fig.  46.    Economic  Reservoir  Dimensions  and  Costs.    Case  16. 


170 


300^30000 


L 


Fig.  47. 


?.  tf<7/2?  <%?«?  /£#*? 

znside   dta.  of  reservoir  in  ft. 

Economic  Reservoir  Dimensions  and  Costs.    Case  2a. 


QOOO    .     .  /oqoo 

instde  dia.  of  reservoir  in  ft 

Fig.  48.     Economic  Reservoir  Dimensions  and  Costs.    Case  26. 


/woo 


171 


172  PRACTICAL  IRRIGATION. 

The  high  cost  of  obtaining  water  naturally  leads  to  economy  in 
its  use.  Owing  to  the  high  cost,  the  greatest  economy  is  practised 
in  the  distribution  of  water  from  pipe  lines  where  irrigation  is 
usually  practised  by  means  of  hose.  In  semi-arid  countries, 
where  the  water  supply  is  limited,  considerable  economy  is  prac- 
tised in  the  use  of  water,  and  very  successful  results  have  been 
attained  by  using  an  average  depth  of  irrigation  of  about  1.25 
inches,  with  an  annual  depth  of  about  1  foot.  Where  the  sup- 
ply is  much  larger,  on  the  contrary,  the  water  is  often  used 
extravagantly.  A  comparison  of  these  figures  with  the  costs, 
as  indicated  for  reservoir  construction,  shows  encouraging  pros- 
pects for  the  possible  storage  of  water  on  a  large  scale. 

The  proper  clearance  to  allow  for  reservoirs  has  been  assumed 
to  be  dependent  merely  upon  the  diameter  of  the  reservoir. 
However,  if  the  reservoir  is  of  large  capacity,  the  depth  of  the 
water,  as  well  as  the  exposure  to  winds,  should  be  taken  into 
consideration  in  assigning  a  suitable  value  to  this  quantity. 
The  top  width  of  the  embankment  has  heretofore  been  assumed 
to  be  4  feet,  but  the  width  of  crown  will  depend  upon  whether 
it  is  desired  to  use  the  top  of  the  embankment  for  a  wagon  road, 
in  which  event  it  should  be  made  considerably  wider.  Practi- 
cally, however,  it  should  be  good  practice  in  construction  of  the 
upper  part  of  an  embankment  where  lined  with  riprap,  to  build 
the  embankment  on  a  steeper  slope  than  lower  down,  in  order 
to  reflect  the  waves.  Thus  it  is  apparent  that  by  the  addition 
of  a  comparatively  small  amount  of  earth  the  top  may  be 
widened  considerably.  In  order  to  see  the  effect  of  increased 
clearance  and  greater  crown,  results  have  been  figured  for  Case 
Ic  with  a  10-foot  crown  and  5-foot  clearance,  assuming  land 
at  $5  per  acre  and  the  value  of  water  input  at  25  cents  per  acre- 
foot.  Also  q  is  taken  as  3.  The  side  slope  continues  the  same 
to  the  top  of  the  embankment. 

In  Case  laa  the  assumptions  are  similar  to  those  in  Case  la 
except  that  q  =  3  instead  of  5,  meaning  a  greater  width  of  rip- 
rap. This  has  no  important  effect  on  the  general  proportions. 

All  tables  so  far  given  for  reservoir  construction  have  assumed 
the  reservoirs  to  be  built  on  level  ground.  As  a  general  rule, 
however,  the  ground  will  have  more  or  less  slope.  It  is  quite 
common  to  find  large  tracts  of  land  where  reservoirs  could  be 
constructed  on  fairly  uniform  slopes.  In  the  appendix,  page  222, 


LARGE   ARTIFICIAL   RESERVOIRS.  173 

is  given  the  mathematical  method  of  determining  economic 
reservoirs  for  sloping  ground.  Cases  Id  and  le  are  for  the 
determination  of  economic  reservoirs  where  the  ground  has  a 
slope  of  1  foot  per  1000  feet,  cost  of  water  input  25  cents  per 
acre-foot,  and  cost  of  land  $5  per  acre.  The  cost  and  proper 
proportions  of  reservoirs  for  these  two  cases  are  given  in  the 
Tables  XXXVII  and  XXXVIII.  Case  Id  is  for  3-foot  clear- 
ance and  4-foot  crown.  Case  le  is  for  5-foot  clearance  and 
10-foot  crown.  The  costs  of  reservoirs  per  acre-foot  output 
refer  merely  to  the  cost  of  construction  of  embankment  and 
riprap,  and  do  not  include  the  cost  of  land.  The  depths  of 
embankments  given  in  these  two  cases  refer  to  mean  depths, 
the  maximum  and  minimum  being  easily  determined  from  the 
slope  of  the  land  and  the  diameter  of  the  reservoirs.  Formulae 
for  sloping  land  apply  only  when  r  X  the  slope  is  less  than  the 
mean  depth  minus  the  clearance.  The  most  economical  reser- 
voir section  on  land  with  much  slope  is  not  the  circular  sec- 
tion. Where  labor  is  not  cheap  and  part  of  the  material  for 
construction  of  the  embankment  has  to  be  hauled  some  dis- 
tance, the  cost  of  such  work  will  be  considerably  over  10  cents. 
In  cases  If,  Ig,  Ih  and  li  a  ground  slope  of  2  feet  per  1000  is 
assumed;  the  cost  of  earthwork  is  25  cents  for  I/  and  Ig,  22 
cents  for  Ih,  and  20  cents  for  li  per  cubic  yard  instead  of  10 
cents;  and  fixed  expenses  12  per  cent  per  year.  In  these  cases 
also  assume  that  a  belt  of  riprap,  t  =  12  feet  wide  and  costing 
90  cents  per  square  yard,  is  laid  around  the  reservoir. 

Cases  I/,  Ig  and  li  assume  4-foot  crown  and  3-foot  clearance. 

Case  Ih  assumes  a  10-foot  crown  and  5-foot  clearance. 

Case  li  assumes  the  reservoir  is  lined  with  a  6-inch  puddle 
mixture  costing  2  cents  per  square  foot. 

Water  supplied  to  reservoir  costs  25  cents  per  acre  foot  in 
If  and  Ih,  and  $2  per  acre-foot  in  Ig  and  li. 

In  case  the  reservoir  will  not  hold  water,  it  may  be  lined  or 
puddled.  The  mathematical  method  of  figuring  the  most 
economical  dimensions  for  a  lined  reservoir  is  given  in  the 
appendix.*  If  the  lining  be  made  of  concrete  or  asphalt,  the 
riprap  would  not  be  used,  and  in  this  event  t  =  0.  Also  under 
these  conditions  much  steeper  inside  slope  can  be  used,  varying 
from  1  to  1,  to  1.5  to  1. 

Case  3A;  is  figured  on  the  assumption  of  a  reservoir  lined  with 

*  See  page  223. 


174 


PRACTICAL  IRRIGATION. 


concrete  costing  90  cents  per  square  yard,  the  cost  of  water 
supplied  to  reservoir  being  $2  per  acre-foot.  The  total  evapora- 
tion and  seepage  losses  are  5  feet  instead  of  6  feet  per  year.  The 
clearance  is  3  feet,  and  the  cost  of  earthwork  is  20  cents  per 
cu.  yd.  The  reservoirs  of  this  class  are  naturally  exceedingly 
deep  in  comparison  with  others.  It  is  frequently  desirable  to 
construct  small  reservoirs  of  this  nature  at  a  minimum  first  cost. 
Formulae  have  been  deduced  (p.  226,  appendix)  to  determine  the 
dimensions  of  the  reservoirs  of  given  capacity  and  minimum 
cost.  These  apply  only  to  large  reservoirs,  and  if  applied  to 
those  less  than  200  feet  in  diameter  may  lead  to  considerable 
inaccuracy.  An  approximate  method  of  applying  these  formulae 
by  the  use  of  a  correction  factor,  is  given  in  the  appendix,  p.  226. 
This  is  fairly  accurate  for  reservoirs  over  100  feet  in  diameter. 
Two  cases  (31  and  3m)  have  been  calculated,  using  this  method 
where  the  cost  of  earthwork  is  taken  as  15  cents  per  cubic  yard, 
and  the  cost  of  the  lining  2  cents  per  square  foot.  The  crown 
is  4  feet  and  the  clearance  in  Case  31  is  1  foot,  and  in  Case  3m 
is  2  feet.  The  results  are  given  in  Tables  XL VI  and  XLVIL 
To  solve  the  general  case  accurately  for  small  reservoirs  would 
involve  quite  complicated  equations. 

TABLES   OF   ECONOMICAL   PROPORTIONS   AND 
COSTS   OF   RESERVOIRS. 

TABLE   XXXIV. 

Case  la. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR  —  25  CENTS. 


Cost  of 

Cost  of 

Diameter 
of  reservoir, 
Feet. 

Depth  of 
embankment, 
Feet. 

Output 
capacity, 
Acre-ft. 

water  per 
acre-ft. 
output 

reservoir 
per  acre-ft. 
output 

Reservoir 
efficiency, 
Per  cent 

capacity 

400 

8.09 

6.03 

$21  .84 

$209  .40 

33 

800 

8.27 

26.20 

9.94 

90.90 

36 

1,200 

8.46 

64.00 

7.29 

64  .90 

38 

1,600 

8.62 

121  .00 

5.52 

47  .50 

40 

2,000 

8.82 

203  .00 

4.43 

37.00 

41 

3,000 

9.21 

520  .00 

3.03 

23.60 

44 

4,000 

9.60 

1,040  .00 

2.32 

17.00 

47 

6,000 

10.31 

2,800  .00 

1.65 

10.90 

52 

8,000 

10.96 

5,730  .00 

1  .32 

8.00 

55 

12,000 

12.15 

15,950  .00 

.98 

5.10 

61 

16,000 

13.20 

33,300  .00 

.83 

3.90 

64 

20,000 

14.18 

59,000  .00 

.73 

3.10 

67 

LARGE   ARTIFICIAL   RESERVOIRS. 


175 


TABLE  XXXV. 

Case  16. 
COST    PER    ACRE-FOOT    SUPPLIED    TO    RESERVOIR  —  $2. 


C*/\ti+  f\f 

Cost  of 

l>i:uneter 
"1  reservoir, 
I-'.-,  -t. 

Depth  of 
embankment, 

Feet. 

Output 
capacity, 
Acre-ft. 

t^o&t  or 

\\  •  :iter  per 
acre-ft. 
output 

reservoir 
per  acre-ft. 
output 
capacity 

Reservoir 
efficiency, 
Per  cent 

400 

9.20 

9.25 

$22  .85 

$177  .00 

44 

800 

10.30 

49.70 

12.52 

81  .70 

52 

1,200 

11.70 

136  .80 

9.18 

52.60 

59 

1,600 

12.15 

283.50 

7.53 

38  .90           61 

2,000 

12.90 

500.00 

6.55 

30  .90           63 

3,000 

14  .50 

1,380  .00 

5.25 

20  .60           68 

4,000 

16.30 

2,970  .00 

4.56 

15.80 

72 

6,000 

19.00 

8,410  .00 

3.88 

11  .00           77 

8,000 

21.30 

17,650  .00 

3.41 

8.50            80 

12,000 

25.30 

50,200  .00 

3.13 

6.10            83 

16,000 

28.50 

104,100  .00 

2.94 

4.90 

85 

20,000 

31  .50 

184,500  .00 

2.81 

4.20 

87 

TABLE   XXXVI. 

/ 

Case  Ic. 
COST   PER   ACRE-FOOT    SUPPLIED   TO   RESERVOIR  —  25   CENTS. 


2,000 

12.20 

303. 

$6.08 

$55  .10 

51 

4,000 

12.80 

1,384. 

3.14 

26.10 

55 

6,000 

13.31 

3,450  . 

2.17 

16.70 

57 

8,000 

13.88 

6,785  . 

1  .70 

12.20 

60 

12,000 

14.87 

17,820  . 

1.22 

7.70 

63 

16,000 

15.80 

38,150  . 

.98 

5.60 

66 

20,000 

16.65 

62,300  . 

.85 

4.40 

68 

TABLE   XXXVII. 

Case  Id. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR  — 25   CENTS. 


2,000 

8.84 

205. 

$4.42 

$36.90 

42 

4,000 

9.74 

1,075. 

2.32 

17.10 

48 

6,000 

10,58 

2,970  . 

1.65 

11  .03 

53 

8,000 

11  .41 

6,240  . 

1.32 

8.16 

58 

12,000 

13.00 

18,180  . 

.99 

5.49 

64 

16,000 

14.40 

38,700  . 

.84 

4.25 

68 

20,000 

16.10 

72,900  . 

.74 

4.25 

72 

176 


PRACTICAL  IRRIGATION. 


TABLE  XXXVIII. 

Case  le. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR  -  25  CENTS. 


Cost  of 

Cost  of 

Diameter 
of  reservoir, 
Feet. 

Depth  of 
embankment, 

Feet. 

Output 
capacity, 
Acre-ft. 

water  per 
acre-t't. 
output 

reservoir 
per  acre-ft. 
output 
capacity 

Reservoir 
efficiency, 
Per  cent 

2,000 

12.25 

306. 

$6.07 

$55  .00 

52 

4,000 

12.84 

1,395. 

3.15 

26.17 

55 

6,000 

13  .53 

3,580  . 

2.17 

16.75 

58 

8,000 

14.24 

7,200  . 

1  .67 

11  .99 

61 

12,000 

15.60 

19,720  . 

1.22 

7  .89 

66 

16,000 

17.00 

41,400. 

.98 

5.79 

69 

20,000 

18.40 

74,600  . 

.86 

4.76 

72 

TABLE  XXXIX. 

Case  2a. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR  — 25   CENTS. 


400 

8.27 

6.53 

$14  .49 

$146  .40 

36 

800 

8.52 

29.10 

7.78 

69.90 

39 

1,200 

8.75 

71.90 

5.23 

44.90 

41 

1,600 

9.00 

138  .30 

3.96 

32.60 

43 

2,000 

9.25 

232  .70 

3.22 

25.50 

45 

3,000 

9.76 

610  .00 

2.22 

16.10 

49 

4.000 

10.26 

1,229.00 

1  .74 

11.70 

52 

6,000 

11  .19 

3,365  .00 

1  .26 

7.50 

56 

8,000 

12.03 

6,950  .00 

1  .03 

5.60 

60 

12,000 

13.52 

19,500  .00 

.79 

3.60 

65 

16,000 

14.85 

40,750  .00 

.68 

2.80 

69 

20,000 

16.02 

72,350  .00 

.60 

2.20 

72 

TABLE   XL. 

Case  2b. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR —  $2. 


400 

10.03 

11  .64 

$16  .49 

$119.90 

50 

800 

11  .15 

59.70 

9.61 

56.60 

56 

1,200 

12.38 

166  .00 

7.26 

36.80 

61 

1,600 

13.45 

346  .00 

6.10 

27.50 

65 

2,000 

14.48 

613  .00 

5.39 

22.00 

68 

3,000 

16.70 

1,735.00 

4.44 

14.90 

73 

4,000 

18  .50 

3,632  .00 

3.94 

14.90 

76 

6,000 

22.20 

10,520  .00 

3.44 

8.20 

80 

8,000 

24.70 

21,600.00 

3.17 

6.30 

83 

12,000 

16.97 

61,050.00 

2.89 

4.60 

86 

16,000 

19.85 

127,000  .00 

2.76 

3.90 

88 

20,000 

22.45 

224,500  .00 

2.64 

3.10 

89 

LARGE    ARTIFICIAL    RESERVOIRS. 


177 


TABLE  XLI. 

Case  If. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR  — 25   CENTS. 


Diameter 
of  reservoir, 
Feet. 

Depth  of 
embankment, 
Feet. 

Output 
capacity, 
Acre-ft. 

Cost  of 
water  per 
acre-ft. 
output 

Cost  of 
reservoir 
per  acre-ft. 
output 
capacity 

Reservoir 
efficiency, 
Per  ceut 

400 

9.95 

11  .4 

$51  .49 

$423 

450 

800 

10.02 

46.4 

25.99 

222 

50 

1,200 

10.13 

107.2 

18.31 

147  .70 

51 

1,600 

10.17 

192  .5 

13.09 

104.30 

51 

2,000 

10.27 

308.0 

10.50 

82.80 

52 

3,000 

10.52 

733.5 

7.06 

54.20 

53 

4,000 

10.81 

1,388 

5.34 

40.05 

55 

6,000 

11.58 

3,564 

3.64 

26.20 

58 

8,000 

12.24 

7,216 

2.81 

19.50 

61 

12,000 

13.97 

20,700 

2.01 

13.25 

67 

16,000 

15.87 

45,500 

1.64 

10.42 

71 

20,000 

17.85 

85,600 

1.43 

8.92 

75 

TABLE   XLII. 

Case  Ig. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR  — $2. 


400 

10.31 

12.44 

$63  .53 

$493 

52 

800 

10.72 

54.6 

28.21 

201 

54 

1,200 

11.14 

133.5 

17.21 

127.20 

56 

1,600 

11.52 

254.6 

14.99 

93.20 

58 

2,000 

11.88 

425 

12.46 

73.10 

60 

3,000 

12.80 

1,104 

9.15 

47.25 

63 

4,000 

13.63 

2,204 

7.51 

35 

66 

6,000 

15.22 

5,980 

5.88 

23.08 

70 

8,000 

16.71 

12,370 

5.07 

17.75 

73 

12,000 

19.72 

35,600 

4.25 

12.67 

77 

16,000 

22.12 

74,500 

3.85 

10.25 

80 

20,000 

24.68 

134,800 

3.61 

8.92 

82 

TABLE   XLIII. 

Case  Ih. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR  — 25  CENTS. 


400 

12.64 

13.4 

$62.49 

So  1C) 

54 

800 

12.71 

54.4 

31  .31 

257 

54 

1,200 

12.79 

124 

20.82 

170 

55 

1,600 

12  .86 

224 

15.73 

126.6 

55 

2,000 

12.96 

358 

12.60 

100.6 

55 

3,000 

13.22 

848 

8.44 

66.1 

56 

4,000 

13.55 

1,596 

6.37 

48.8 

58 

6,000 

14.31 

4,095 

4.08 

30.2 

61 

8,000 

15.19 

8,288 

3.28 

23.7 

64 

12,000 

17.27 

24,100 

2.30 

15.9 

70 

16,000 

19.61 

53,600 

1  .86 

12  .4 

74 

20,000 

22.06 

101,500 

1.62 

10.6 

78 

ITS 


PRACTICAL  IRRIGATION. 


TABLE   XLIV. 

Case  li. 
COST  PER  ACRE-FOOT  SUPPLIED  TO  RESERVOIR 


—  $2. 


Cost  of 

Cost  of 

Diameter 
of  reservoir, 
Feet. 

Depth  of 
embankment, 
Feet. 

Output 
capacity, 
Acre-ft. 

•water  per 
acre-ft. 
output 

reservoir 
per  acre-ft. 
.    output 
capacity 

Reservoir 
efficiency, 
Per  cent 

400 

14.9 

25.3 

$41  .18 

$380 

69 

800 

18.0 

138 

24.20 

214 

75 

1,200 

20.5 

377 

18.35 

157 

78 

1,600 

22.8 

775 

15  .29 

127 

81 

2,000 

24.8 

1,356 

13  .37 

108.3 

82 

3,000 

29.2 

3,750 

10.68 

82.4 

85 

4,000 

32.9 

7,752 

9.24 

68.7 

87 

6,000 

39.2 

21,600 

7.66 

53.6 

89 

8,000 

44.6 

44,600 

6.80 

45.4 

90 

12,000 

54.0 

124,600 

5.79 

35.8 

92 

16,000 

61  .9 

258,000 

5.24 

30.6 

93 

20,000 

69.0 

455,000 

4.87 

27.1 

94 

Case  4a. 
COST  PER  ACRE-FOOT  SUPPLIED   TO   RESERVOIR  — 25   CENTS. 


400 

8.1 

5.9 

$20.78 

$198.70 

34 

800 

8.3 

26.7 

8.83 

79.90 

38 

1,200 

8.6 

66.6 

5.89 

51.10 

39 

1,600 

8.8 

129.8 

4.47 

37.40 

41 

2,000 

9.0 

219 

3.65 

29.50 

43 

3,000 

9.6 

583 

2.53 

18.00 

47 

4,000 

10.1 

1,178 

1.99 

14.10 

51 

6,000 

11.0 

3,260 

1.45 

9.30 

56 

8,000 

11.9 

6,775 

1.18 

7.00 

60 

12,000 

13.4 

19,200 

.91 

4.70 

65 

16,000 

14.5 

39,250 

.78 

3.70 

68 

20,000 

15.8 

70,800 

.70 

3.10 

71 

Case  laa. 
COST  PER  ACRE-FOOT  SUPPLIED   TO  RESERVOIR  — 25  CENTS. 


400 

8.6 

7.6 

$22.70         I  $219.30 

39 

800 

8.9 

32.2 

11.40              106.60 

41 

1,200 

8.9 

'       76.2 

7.66 

69.50 

42 

1,600 

9.1 

143.0 

5.77 

50.80 

44 

2,000 

9.3 

236 

4.65 

39.90 

45 

3,000 

9.6 

590 

3.17 

25  50 

47 

4,000 

10.0 

1,156 

2.44 

18.50 

50 

6,000 

10.7 

3,042 

1.73 

11.90 

53 

8,000 

11.3 

6,128 

1.36 

8.60 

57 

12,000 

12.4 

16,620 

1.02 

5.70 

61 

16,000 

13.5 

34,560 

.85 

4.20 

65 

20,000 

14.4 

60,800 

.74 

3.30 

68 

LARGE   ARTIFICIAL   RESERVOIRS. 


179 


One  other  case  (No.  4a)  of  reservoir  construction  will  be  con- 
sidered based  on  certain  data  compiled  by  Professor  Fortier, 
which  the  following  statements  will  explain.  The  general 
assumptions  of  this  case  are  similar  to  those  in  Case  la,  except 
that  the  side  slopes  and  widths  of  embankment  at  top  are 
different,  as  will  be  explained. 

As  has  been  pointed  out,  the  proper  section  of  the  banks  of 
earth  reservoirs  depends  on  the  depth  of  water,  exposure  to 
winds,  and  on  the  material  of  which  the  embankment  is  com- 
posed. The  inner  and  outer  slopes  must  not  be  so  steep  that 
they  will  not  stand  up  under  the  action  of  waves  or  of  the  ele- 
ments. The  top  of  the  embankment  must  have  sufficient 
clearance  above  the  water  plane  not  to  allow  the  waves  to  wash 
over  it.  The  particular  conditions  of  each  case  should  be  given 
individual  consideration.  It  is  well  to  take  into  consideration 
the  practice  in  existing  earth  reservoirs. 

In  bulletin  No.  46  of  the  Agricultural  College  Experiment 
Station  at  Logan,  Utah,  Prof.  S.  Fortier  gives  some  interesting 
figures  on  earth  embankments  for  reservoirs.  From  75  typical 
earth  reservoirs,  the  following  figures  were  obtained : 

The  inner  slopes  varied  from  4: 1  to  1: 1,  averaging  2.61: 1. 

The  outer  slopes  averaged  2.1: 1. 

The  following  table  gives  a  summary  of  these  results: 

SLOPE  OF  RESERVOIR  EMBANKMENTS. 


No.  of  Reservoirs 

Outer  Slope 

No.  of  Reservoirs 

Inner  Slope 

2 

1:  1 

2 

1:  1 

23 

1-i:  1 

23 

H:  1 

2 

2 

lf:l 

41 

2: 

31 

2:1 

1 

2-i: 

1 

2-4:1 

3 

2-i: 

1 

2-f:l 

3 

3: 

11 

3:  1 

Average 

2.1: 

2 

4:  1 

Average 

2.61:  1 

From  the  same  reservoirs  it  is  deduced  that  the  thickness  in 
feet  of  embankment  at  the  high  water  line  is  5  plus  the  depth  of 
water  in  the  reservoir. 

In  Case  4a  the  following  assumptions  are  made:  S  =  2.61, 
p  =  2.1,  W  =  H  +  5  -  26T7,  6=3. 

In  the  practical  construction  of  an  earth  embankment,  Pro- 
fessor Fortier  advocates  the  use  of  a  core  wall.  A  very  effective 


180 


PRACTICAL  IRRIGATION. 


TABLE  XLV. 

Case  3k. 
COST   PER   ACRE-FOOT   SUPPLIED    TO    RESERVOIR  —  $2, 


Diameter 
of  reservoir, 
Feet. 

Depth  of  em- 
bankment, 
Feet. 

Output 
capacity, 
Acre-ft. 

Cost  of  water 
per  acre-f  t. 
output 

400 
800 
1,200 
1,600 
2,000 
3,000 
4,000 
6,000 

27.5 
37.7 
45.4 
52.1 
58 
70.3 
80.8 
98.5 

65 
378 
1,050 
2,175 
3,820 
10,620 
21,880 
60,750 

$47  .20 
29.36 
23.10 
19.66 
17.45 
14.20 
12.40 
10.32 

TABLE   XLVI. 

Case  31. 
LINED   RESERVOIRS  CONSTRUCTED   FOR   MINIMUM  FIRST  COST. 


Mean  diam- 
eter bank, 
Feet. 

Depth 
of  bank, 
Feet. 

Acre-ft. 
capacity 

Cost  per 
acre-t't. 

Total 
cost 

40 

4.49 

.0487 

$1,232 

$60 

80 

6.13 

.395 

551 

217 

120 

7.40 

1.23 

381 

468 

160 

8.45 

2.69 

300 

808 

200 

9.42 

4.94 

252 

1,245 

300 

11  .45 

14.48 

187 

2,730 

400 

13.13 

30.70 

156 

4,785 

TABLE   XL VII. 
Case  3m. 


40 

5.45 

.038 

$1,906 

$73 

80 

7.00 

.352 

698 

246 

120 

8.23 

1  .141 

453 

515 

160 

9.28 

2.54 

347 

882 

200 

10.20 

4.67 

287 

1,339 

300 

12.22 

13.9 

209 

2,900 

400 

13.90 

29.7 

169 

5,028 

method  of  building  the  center  of  the  embankment  is  to  keep  the 
central  portion  during  construction  lower  than  the  two  sides,  so 
as  to  leave  a  small  ditch  in  the  center.  This  is  kept  partially 
full  of  water;  during  the  day  the  water  is  quite  low,  not  to 
interfere  with  working,  and  at  night  the  water  level  is  raised. 

The  construction  of  an  embankment  impervious  to  water 
involves  in  the  main,  the  proper  arrangement  of  various  sizes 
of  soil  grains,  the  effective  filling  of  interstices,  the  consequent 


LARGE   ARTIFICIAL   RESERVOIRS. 


181 


TABLE  XLVIII. 

COST    OF    RESERVOIR    CONSTRUCTION    PER    ACRE-FOOT- 
AMERICAN    RESERVOIRS. 

(Taken  from   Schuyler's    "  Reservoirs  for  Irrigation,  Water  Power  and 
Domestic  Water  Supply.") 


No. 

Name 

Character  of  dam 

Capacity  of 
reservoir, 
Acre-ft. 

Cost 

Cost  per 
acre-ft. 

1 
2 
3 

4 
6 

7 

Sweet  water  dam,  Cal. 
Bear  Valley  dam,  Cal. 
Hemet  dam,  Cal.  .    . 
Escondido  dam,  Cal. 
La  Mesa  dam,  Cal.    . 
Cuyamaca  dam,  Cal 

Masonry  .... 
Masonry  .... 
Masonry  .... 
Rock-fill  .... 
Hydraulic-fill  .  . 
Earth  .  .  . 

22,566 
40,000 
10,500 
3,500 
1,300 
11,410 

$264,500 
68,000 
150,000 
110,059 
17,000 
54,400 

$11.72 
1.70 
14.29 
31.44 
13.10 
4  76 

g 

Buena  Vista  Lake,  Cal 

Earth  .  ... 

170,000 

150,000 

88 

10 
11 
12 
13 

14 
15 

16 

17 

18 

English  dam,  Cal.      . 
Bowman  dam,  Cal.    . 
San  Leandro  dam,  Cal. 
Eureka    Lake    dam, 
Cal. 
Fancherie  dam,  Cal. 
Lake  Avalon,  Pecos 
River,  N.M. 
Lake  McMillan,  Pecos 
River,  N.M. 
Tyler,  Texas      .    .    . 
Cache  la  Poudre  Col 

Rock-fill  crib  .  . 
Rock-fill  crib  .  . 
Earth  
Rock-fill  .... 

Rock-fill  .... 
Rock-fill  and  earth 

Rock-fill  and  earth 

Hydraulic-fill  .  . 
Earth 

14,900 
21,070 
13,270 
15,170 

1,350 
6,300 

89,000 

1,770 
5  654 

155,000 
151,521 
900,000 
35,000 

8,000 
176,000 

180,000 

1,140 
110  266 

10.40 
7.19 
68.00 
2.32 

5.92 
27.94 

2.02 

.64 
19  50 

19 

Larimer   and    \Veld, 

Earth 

11  550 

89,782 

7  77 

20 
21 

Col. 
Windsor,  Col.     .    .    . 
Monument,  Col 

Earth  
Earth  

23,000 

885 

75,000 
33,121 

3.26 
38  69 

22 
23 

Apishapa,  Col.  .    .    . 
Hardsc  rabble  Col 

Earth  
Earth 

459 
102 

14  772 
9  997 

32.18 
97  78 

?4 

Boss  Lake,  Col.     .    . 

Earth  

205 

14,654 

71  .39 

?f> 

Saguache,  Col.  .    .    . 

Earth  

954 

30,000 

31.45 

26 
27 

Seligman,  Ariz.  .    .    . 
Ash  Fork,  Ariz 

Masonry  .... 
Steel  .... 

703 
110 

150,000 
45,776 

169.50 
416  30 

28 
29 
30 
31 

Williams,  Ariz.      .    . 
Walnut  Canon,  Ariz. 
New  Croton,  N.Y.     . 
Titicus,  N.Y.     .    .    . 

Masonry  .... 
Masonry  .... 
Masonry  and  earth 
Masonry  and  earth 

338 
480 
98,200 
22,000 

52,838 
55,000 
4,150,573 
933,065 

156.35 
114.60 
42.27 
42.42 

32 

Sodom  NY 

Masonry  and  earth 

14,980 

366,990 

24  50 

W 

Bog  Brook  N  Y 

Earth  

12,720 

510,430 

40.12 

34 
35 

Indian  River,  N.Y. 
Wigwam,  Conn.     .    . 

Masonry  and  earth 
Masonry  .... 

102,548 
1,028 

83,555 
150,000 

.81 
145.90 

Total 

730  012 

9  296,439 

Average 

12.71 

Mean  capacity 

22,100 

Average  capacity  exclusive  of  No.  8,  17,500  acre-feet. 
Average  cost  per  acre  foot  exclusive  of  No.  8,  $16.32. 


182 


PRACTICAL  IRRIGATION. 


TABLE  XLIX. 
DATA    CONCERNING    AMERICAN    RESERVOIRS. 


Rated 

Name 

Surface 
area, 
Acres 

Maxi- 
mum 
height, 
Feet 

Rated 
capacity, 
Acre-ft. 

Corrected 
capacity, 
Acre-ft. 

Cost  per 
acre-ft. 
corrected 
capacity 

capa- 
city, 
divided 
by 
surface 

area, 

Feet 

1   Sweetwater   .    .    . 

895 

76 

22,566 

19,881 

$13.30 

27.0 

2  Bear  Valley  .    .    . 

3,300 

80 

40,000 

30,000 

2.20 

12.0 

3  Hemet    

738 

150 

10,500 

8,286 

18.05 

14.0 

4   Escondido      .    .    . 

285 

110 

3,500 

2,645 

41.70 

12.0 

5   Lower  Otay  .    .    . 

1,414 

150 

42,190 

37,948 

30.0 

6  La  Mesa     .... 

70 

140 

1,300 

1,090 

15  '.60 

19.0 

7   Cuyamaca     .    .    . 
8   Buena  Vista      .    . 

959 
25,000 

35 
10 

11,410 
170,000 

8,533 
95,000 

5.50 
1  .56 

13.0 
6.8 

12   San  Leandro     .    . 

715 

170 

2,145 

13,270 

74.20 

19.0 

expulsion  of  the  air  therefrom,  and  the  protection  of  the  banks 
from  extreme  drought  or  saturation.  Professor  Fortier  con- 
siders that  the  construction  of  the  embankment  as  outlined 
gives  most  satisfactory  results,  since  there  is  no  method  of 


.^^,  £000-  3000  WOO  .  5000^ 

output  capa'citj/  in  acre-ft 

Fig.  49.     First  Costs  of  Artificial  and  Natural  Reservoirs. 

arrangement  and  compacting  of  the  soil  grains,  which  will  give 
results  superior  to  those  attained  by  the  use  of  water. 
Table  XL VIII,  which  shows  the  cost  of  American  reservoirs, 


LAR<;E  .  i  R  n  FK  7.  t  /,  KESER  voutx. 


183 


makes  no  allowance,  however,  for  loss  by  evaporation.  In  the 
majority  of  natural  reservoirs  the  storage  capacity  per  foot  of 
depth  increases  very  rapidly  toward  the  highest  water  level,  the 
lower  part  of  the  reservoir  being  of  comparatively  little  value  as  a 
storage  basin.  In  consideration  of  the  evaporation  we  would  be 
more  nearly  correct  if  we  assume  the  top  area  as  subject  to  evapo- 
ration rather  than  the  area  obtained  by  dividing  the  total  capacity 
stored  by  the  maximum  depth.  Since  the  greater  part  of  the 


s  eve 


slope  2 


Fig.  50.     First  Cost  of  Artificial  and  Natural  Reservoirs. 

storage  is  in  the  upper  part  of  the  reservoir  a  much  greater  sur- 
face will  be  presented  for  evaporation  during  the  greater  part  of 
the  time.  In  order  to  correspond  as  closely  as  possible  with  the 
basis  of  figures  for  earth  reservoirs,  Table  XLIX  has  been  calcu- 
lated, assuming  that  the  actual  reservoir  capacity  for  storage  is 
diminished  by  3  feet  times  the  surface  area  of  the  reservoir. 

In  Table  XLIX  is  also  given  a  column  showing  the  quotient 
arising  from  dividing  the  rated  reservoir  capacity  by  the  surface 
area.  Figs.  49  and  50  show  the  relation  between  the  cost  of 
reservoir  construction  per  acre-foot  output  and  the  output 
capacity  of  the  reservoir  in  acre-feet.  The  curves  are  drawn 
for  Cases  l,-a-c-d-e-f-g-h.  On  the  diagrams  are  also  plotted 
points  representing  the  relation  between  the  cost  of  reservoir 


184  PRACTICAL  IRRIGATION. 

construction  per  acre-foot  and  the  reservoir  capacity  as  given 
in  Schuyler's  tables,  these  points  being  denoted  by  black  points 
surrounded  by  small  circles  and  numbered  to  correspond  to  the 
numbers  in  the  table.  In  the  cases  in  which  surface  areas  are 
given  (Table  XLIX) ,  points  are  also  given  denoting  the  relation 
between  the  reservoir  output  capacity  and  the  cost  per  acre- 
foot  output.  These  points  are  denoted  by  small  crosses. 
Several  points  are  not  plotted  on  the  diagram,  as  they  are  far 
beyond  the  range,  owing  to  very  high  cost  of  construction.  It 
will  be  noted  that  the  greater  part  of  the  natural  reservoirs 
exceed  considerably  in  cost  per  acre-foot  the  cost  of  construc- 
tion of  earthen  reservoirs  of  corresponding  size.  On  the  dia- 
gram is  also  given  a  point  marked  "  average, "  which  indicates 
the  relation  between  the  average  size  of  reservoirs  in  Table 
XL VIII  as  determined  by  dividing  the  gross  capacity  by  the 
number  of  reservoirs,  and  the  average  cost  per  acre-foot  as 
determined  by  dividing  the  total  cost  by  the  total  number  of 
acre-feet.  This  point  indicates  that  in  round  numbers  these 
reservoirs  cost  2.5  times  as  much  as  corresponding  earthen 
reservoirs  in  Cases  1,-a-d,  and  about  80  per  cent  more  than  cor- 
responding reservoirs  in  Cases  ^,-°~ej  an(l  about  the  same  as 
Case  I/. 

It  is  to  be  noted  particularly  that  in  the  cases  assumed  for 
earth  reservoirs  no  allowance  whatever  has  been  made  for  taking 
advantage  of  the  natural  lay  of  the  land  in  aiding  in  obtaining 
storage  capacity.  Where  an  artificial  reservoir  several  square 
miles  in  area  is  to  be  built,  it  will  undoubtedly  be  possible  in 
many  cases  to  obtain  very  material  advantage  by  the  use  of 
natural  sites,  contributing  greatly  to  the  reservoir  storage 
capacity.  In  fact,  should  the  irrigable  land  lie  in  such  a  way  that 
only  part  of  the  reservoir  could  be  used  for  gravity  irrigation,  it 
might  easily  pay  to  install  a  pumping  plant  for  taking  water 
from  the  lowrer  part  of  the  reservoir  rather  than  to  construct  a 
reservoir  of  considerably  greater  depth.  A  general  study  of 
reservoir  construction  by  means  of  earthen  embankments 
brings  out  the  importance  from  a  construction  standpoint  of 
comparatively  shallow  reservoirs,  thus  leading  to  considerable 
percentage  losses  by  evaporation.  In  round  numbers,  in  the 
great  majority  of  cases  considered,  earthen  reservoirs  will  lose 
20  to  60  per  cent  of  the  water  which  flows  into  them,  whereas 


LARGE   ARTIFICIAL   RESERVOIRS.  185 

the  natural  reservoirs  referred  to  will  lose  but  15  to  30  per  cent 
of  their  water  from  this  same  cause.  Where  the  percentage  of 
evaporation  losses  is  considerable,  it  is  important  that  the 
reservoir  be  made  of  such  a  size  that  there  will  be  an  ample 
supply  of  water  to  fill  it  during  the  season,  for  obvious  reasons. 
It  would  appear  that  the  construction  of  earthen  reservoirs, 
if  the  attendant  conditions  have  been  carefully  studied,  should 
prove  a  most  important  aid  in  the  development  of  the  country. 

Many  of  the  natural  reservoirs  have  been  constructed  with 
masonry  dams  at  an  exceedingly  high  cost  per  acre-foot  of 
capacity.  The  type  of  construction  employed  is  often  largely 
governed  by  the  conditions  of  service  to  which  the  dam  will  be 
subjected,  such  as  excessive  floods,  necessitating  the  best  kind 
of  construction.  Even  then  it  is  not  uncommon  for  floods  of 
extraordinary  violence  to  do  considerable  damage  to  dams. 
These  points  must  be  taken  into  consideration  in  allowing  a 
suitable  figure  for  depreciation.  An  earthen  reservoir,  on  the 
contrary,  in  most  cases  may  be  constructed  where  the  danger 
from  floods  is  practically  absent,  and  where,  if  conditions  are  at 
all  favorable,  sedimentation  of  the  reservoir  may  be  largely 
avoided  by  means  of  proper  sand  traps  in  the  supply  canal. 

In  some  cases,  however,  earthern  reservoirs  are  so  located 
that  it  is  difficult  to  afford  them  complete  protection  against 
the  danger  of  floods  without  incurring  great  expense.  For  eco- 
nomic reasons,  earth  reservoirs  are  usually  constructed  of  the 
material  near  at  hand.  The  proper  dimensions  of  the  banks 
will  depend  largely  on  the  nature  of  their  composition,  and  a 
suitable  design  calls  for  the  exercise  of  good  engineering  judg- 
ment. Earth  embankments  should  preferably  be  constructed 
with  the  coarser  material  near  the  outer  edge,  so  that  whatever 
water  seeps  through,  the  inner  side  of  the  embankment  will 
drain  away  readily,  and  not  saturate  the  entire  embankment, 
and  render  it  liable  to  slip.  The  more  impervious  material 
should  be  arranged  in  the  center,  or  nearer  the  inner  side.  A 
core  wall  in  the  center  of  an  embankment  adds  a  large  factor  of 
safety,  protecting  against  gophers,  and  other  burrowing  animals, 
and  adding  materially  to  the  imperviousness  to  water,  and  con- 
sequent diminution  of  both  the  loss  by  seepage  and  risk  of 
failure.  Puddle  is  usually  used  for  such  a  purpose,  though 
often  a  concrete  wall,  two  or  three  feet  thick,  is  employed. 


186  PRACTICAL  IRRIGATION. 

No  reservoir  is  immune  from  the  danger  of  damage,  and 
unprecedented  conditions  of  rainfall,  etc.,  have  in  some  cases 
wrought  considerable  damage  to  such  structures.  Failures 
have  occurred  in  dams  and  embankments  of  all  descriptions, 
due  either  to  conditions  difficult  to  foresee,  or  to  faulty  con- 
struction. In  properly  designed  dams,  where  the  attendant 
conditions  have  been  thoroughly  studied,  the  danger  of  failure 
is  exceedingly  small.  It  is  probable  that  a  properly  constructed 
masonry  dam  offers  less  danger  of  failure  than  a  well  built  earth 
embankment.  Of  course  in  reservoirs  built  entirely  in  embank- 
ment, the  greatly  increased  length  of  embankment  adds  to  the 
chance  of  failure.  Experience  with  the  large  number  of  earth 
reservoirs  indicates  that  when  conditions  are  at  all  favorable, 
when  the  construction  is  good,  and  when  precautions  are  taken 
to  prevent  the  water  exceeding  the  proper  depth,  this  type  of 
construction  is  reliable,  and  is  of  great  economic  benefit. 


CHAPTER  XV. 

LARGE    RESERVOIRS    FOR    THE    STORAGE    OF 
ARTESIAN    WATER. 

THE  conditions  governing  the  supply  of  water  from  an  artesian 
well  are  different  in  many  respects  from  those  governing  the 
supply  of  river  or  rain  water,  and  in  consequence  reservoir 
construction  to  retain  part  of  this  supply  for  irrigation  requires 
special  consideration  of  the  various  features  of  the  case.  In  the 
case  of  artesian  wells,  the  flow  of  the  water  may  be  considered 
as  practically  constant.  This  does  not  mean  that  in  one  year 
it  may  not  be  somewhat  different  from  its  value  in  another 
year,  due  to  the  possible  causes  enumerated;  but  for  any  con- 
siderable period,  the  output  of  the  wells  when  the  water  supply 
is  under  considerable  head  may  be  regarded  as  uniform,  provided 
that  excessive  development  of  wells  does  not  affect  the  water 
pressure.  The  possible  effect  of  this  contingency  should  always 
be  taken  into  consideration  when  planning  a  storage  reservoir 
for  artesian  wells. 

In  most  places  where  artesian  wells  occur,  there  are  practi- 
cally no  natural  reservoir  sites  available,  and  in  order  to  store 
water  the  entire  reservoir  must  be  constructed  artificially.  In 
many  districts  wells  were  originally  sunk  for  a  supply  of  stock 
water,  and  the  flow  from  them  has  in  some  places  formed  large, 
shallow  pools  totally  unsuitable  for  irrigation  purposes,  due  to  the 
elevation  being  lower  than  the  surrounding  land,  the  shallow 
depth  also  presenting  an  unduly  great  surface  for  evaporation. 

The  question  to  be  solved  by  the  irrigator  is,  What  capacity, 
and  what  size  and  dimensions,  would  it  pay  to  make  the  reser- 
voir for  the  storage  of  artesian  well-water  when  the  supply 
comes  from  a  well  delivering  a  given  flow?  As  the  entire  flow 
of  the  well  may  be  obtained  at  no  greater  cost  than  part  of  the 
supply,  the  natural  suggestion  is  to  build  a  reservoir  of  sufficient 
capacity  to  retain  the  output  of  the  well  between  irrigation 
seasons.  There  are  many  practical  limitations  to  the  size  of 

187 


188  PRACTICAL  IRRIGATION. 

reservoirs  for  wells,  since  on  the  one  hand  evaporation  and 
seepage  play  a  most  important  part  in  determining  the  dimen- 
sions of  the  reservoirs,  tending  to  call  for  a  greater  depth  of 
water;  and  on  the  other  hand,  if  the  reservoir  is  made  exceed- 
ingly deep,  the  additional  depth  against  which  the  well  has  to 
operate  may  cut  down  very  materially  the  discharge.  This 
suggests  one  important  point  about  artesian  wells,  namely, 
that  the  discharge  of  the  well  should  be  subjected  to  as  little 
hydrostatic  pressure  as  possible.  Artesian  pressure  will  raise 
the  water  without  flow  to  a  certain  height  above  the  ground 
level,  known  as  the  static  head.  If  this  static  head  is  large,  a 
few  feet  additional  pressure  against  the  well  will  not  have  a  great 
effect  on  the  discharge;  but  should  the  static  head  be  com- 
paratively small,  the  additional  pressure  of  a  few  feet  of  water 
will  materially  affect  the  output.  The  pipe  supplying  water  to 
the  reservoir  should  not  be  taken  over  the  top  of  the  embank- 
ment to  let  the  water  fall  into  the  reservoir.  Rather  take  it 
into  the  lower  part,  in  order  that  the  maximum  pressure  operat- 
ing against  the  artesian  flow  may  be  as  small  as  possible  for  as 
long  a  time  as  possible.  Also  in  this  same  connection,  an  outlet 
should  be  provided  from  the  well  on  to  the  ground  direct,  and  a 
valve  inserted  to  cut  off  the  reservoir  from  this  pipe,  so  that 
when  it  is  desired  to  irrigate,  the  well  water  will  be  delivered 
under  a  still  lower  hydrostatic  pressure  than  if  it  were  necessary 
to  overcome  the  difference  in  elevation  between  the  ground  and 
the  top  of  the  water  in  the  reservoir.  At  the  same  time,  the 
reservoir  water  can  be  added  to  the  water  from  the  well,  and 
used  in  irrigation. 

In  the  consideration  of  the  problem  of  reservoir  dimensions 
for  artesian  wells,  the  assumption  will  be  made  that  during  the 
irrigation  period  there  will  be  a  certain  time  during  which  the 
well  supply  which  will  not  be  used  directly  on  the  ground  for 
irrigation,  owing  to  rainfall  or  other  causes,  will  be  stored  in  the 
reservoir.  In  order  to  simplify  the  problem,  which  would 
otherwise  be  quite  complicated,  further  assumption  will  be  made 
that  the  flow  of  the  well  is  constant  and  is  not  affected  by  the 
static  pressure  due  to  the  water  in  the  reservoir.  The  problem 
to  be  solved,  then,  is:  Under  these  conditions  what  size  and  con- 
struction of  reservoir  will  give  the  cheapest  total  annual  cost  of 
all  water  used  for  irrigation,  including  both  the  output  of  the 


STORAGE   OF   ARTESIAN    WATER. 


189 


reservoir  and  the  water  from  the  well  which  is  used  directly 
on  the  land?  Obviously  the  construction  of  a  reservoir  will 
depend  on  many  considerations,  among  which  are  the  flow  of 
the  well,  the  annual  cost  of  the  well  per  gallon  per  minute,  the 
irrigation  factor  without  the  use  of  the  reservoir,  the  season  of 
the  year  during  which  irrigation  is  desired,  seepage  and  evapora- 
tion, rainfall,  as  well  as  the  cost  of  construction  of  the  reservoir 
itself.  For  a  consideration  of  this  last  item  it  is  first  necessary  to 
determine  the  cost  per  acre-foot  of  the  well  water  supplied  from 
the  well.  The  flow  of  1  gallon  per  minute  will  deliver  1.612  acre- 
feet  ,per  year.  In  estimating  the  cost  of  water  furnished  by  an 


«35 


n 


1 


\& 


.      ¥  6, 

cost  f>er-   acre-/c. 


.6 
otfc. 


10 


Fig.  51.    Cost  of  Well  Water  per  Acre-foot. 

artesian  well,  the  method  to  be  followed  is  to  figure  first  the  cost 
of  the  well  per  gallon  per  minute,  as  already  outlined,  and  then 
to  assume  twelve  per  cent  per  year  on  the  investment  to  be  the 
cost  of  obtaining  water  from  the  well.  Multiplying  the  cost  of 
well  per  gallon  per  minute  by  0.12  gives  the  annual  cost  per 
gallon  per  minute.  Dividing  the  result  by  1.612  gives  the 
cost  per  acre-foot  of  water.  Without  storage,  well  water  is 
used  for  only  a  limited  portion  of  the  year.  The  irrigation 
factor  for  the  well  represents  the  total  percentage  of  time  when 
the  well  water  is  in  use.  The  cost  per  acre-foot  just  mentioned, 
refers  to  the  100  per  cent  irrigation  factor.  To  ascertain  the 
cost  of  the  well  water  for  any  other  irrigation  factor,  divide  this 
cost  by  the  irrigation  factor.  Fig.  51  and  Table  L  give  a  tab- 
ulation and  graphical  representation  of  the  result  of  this  method 


190 


PRACTICAL  IRRIGATION. 


of  calculation.  The  annual  cost  of  most  artesian  wells  in  Texas 
per  acre-foot  of  water  is  between  25  cents  and  $2.  At  a  25  per 
cent  irrigation  factor  this  would  make  the  cost  of  water  used 
without  storage  between  SI  and  $8  per  acre-foot  per  year. 

The  use  of  reservoirs  as  a  storage  for  water  has  the  additional 
advantage  of  utilizing  to  the  utmost  the  resources  of  the  country 
and  of  providing  water,  even  though  at  a  rather  high  apparent 
cost,  which  might  otherwise  not  be  supplied. 

Let  U  equal  the  irrigation  factor  without  a  reservoir,  then  the 
quantity  of  water  supplied  annually  by  the  well  would  be  repre- 

H  —C 

sented  by  a  depth  in  the  reservoir  of  — —  and  the  quantity 

of  water  actually  used  would  be  represented  by 


H  -  B  +  (H  -  C) 


1-U 


In  the  Appendix,  page  227,  is  given  the  mathematical 
method  of  arriving  at  the  best  section  of  the  reservoir.  It  is 
to  be  noted  that  this  method  does  not  provide  the  most  economi- 
cal reservoir  to  retain  a  given  supply  of  water,  but  it  does  provide 

TABLE  L. 
THE  COST  OF  WELL  WATER. 


Well, 

$        Cost  per  acre-ft.  per  year  for  irrigation  factor 

cost  per 

gal.  per 

rain. 

10O. 

50. 

40. 

30. 

25. 

20. 

15. 

10. 

1 

.07 

.15 

.19 

.25 

.30 

.37 

.49 

.74 

2 

.15 

.30 

.37 

.50 

.60 

.74 

.99 

1.49 

3 

.22 

.45 

.56 

.74 

.89 

1.12 

1.49 

2.23 

4 

.30 

.60 

.75 

.99 

1.19 

1.49 

1.98 

2.98 

5 

.37 

.74 

.93 

1.24 

1.49 

1.86 

2.48 

3.72 

6 

.45 

.89 

1  .12 

1  .49 

1.79 

2.24 

2.98 

4.47 

7 

.52 

1  .04 

1  .30 

1  .74 

2.08 

2.61 

3.48 

5.21 

8 

.60 

1  .19 

1  .49 

1  .99 

2.38 

2.98 

3.97 

5.96 

9 

.67 

1.34 

1.68 

2.23 

2.68 

3.35 

4.47 

6.70 

a  reservoir  of  such  proportions  that  the  total  acre-feet  of  water 
(A)  furnished  by  the  well  direct  to  the  ground  and  by  the  out- 
put of  the  reservoir  shall  be  furnished  at  a  minimum  cost,  when 
the  cost  per  acre-foot  of  water  supplied  from  the  well,  and  also 


STORAGE    OF   ARTESIAN    WATER. 


191 


the  corresponding  capacity  of  the  well  are  known.  In  arriving 
at  a  solution  of  this  problem,  the  cost  per  acre-foot  output  of 
the  well  is  taken  as  the  cost  at  100  per  cent  irrigation  factor. 

Tables  LI  to  LVIII  illustrate  the  results  of  these  determina- 
tions for  reservoirs  with  clearances  of  3  feet,  and  Tables  LIX  to 


wo 


GOO 


'<$,***  *8?°*  lase'Sftt. 


1200 


Fig.  52.    Economic  Well  Reservoirs.     Case  E2. 

LX  VI  illustrate  the  same  thing  for  reservoirs  with  2-ft.  clearance. 
In  all  cases  the  cost  of  the  land  is  taken  as  $15  per  acre.  The 
cost  of  water  supplied  by  the  well  in  Cases  A,  C,  E,  and  G  is  $2, 


VOO 


GOO  800     .  '.("XL 

inside  dia.  cf  &ase  in  ft. 

Fig.  53.     Economic  Well  Reservoirs.     Case  G2. 

and  in  Cases  B,  D,  F,  and  H  is  25  cents  per  acre-foot.  Cases  A,  B, 
E,  and  F  are  for  reservoirs  with  banks  riprapped,  and  Cases  C,  D, 
G,  and  H  are  for  banks  without  riprap.  The  results  in  Cases 


192  PRACTICAL  IRRIGATION. 

E2  and  G2  are  illustrated  in  curves,  Figs.  52  and  53.  Curve 
No.  1  represents  the  relations  existing  between  the  reservoir 
inside  diameter  and  the  total  capacity,  A,  in  acre-feet.  Curve 
No.  2  represents  the  relation  between  the  inside  diameter  and 
the  depth  of  the  embankment.  Curve  No.  3  represents  the 
relation  between  the  inside  diameter  and  the  cost  of  the  reser- 
voir construction  per  acre-foot  of  water  used,  and  No.  4  repre- 
sents the  relation  between  the  inside  diameter  of  the  reservoir 
and  the  annual  cost  per  acre-foot  of  the  water  used  for  irrigation. 
Curve  No.  5  represents  the  relation  between  the  inside  diameter 
of  the  reservoir  and  flow  in  gallons  per  minute  of  the  well 
supplying  the  same.  These  tables  are  all  based  on  an  irriga- 
tion factor  of  25  per  cent,  annual  seepage  and  evaporation,  6  feet, 
rainfall,  2  feet,  seepage  and  evaporation  during  the  irrigation 
season,  3  feet;  water  supplied  from  the  wells  to  the  reservoir 
during  the  irrigation  season,  1  foot  in  depth.  Cases  1  and  2 
refer  to  the  slopes  of  the  bank,  as  already  outlined. 

The  reservoir  efficiency  given  in  Tables  LI  to  LXVI  represents 
the  ratio  of  the  water  put  into  the  reservoir  to  that  which  is  taken 
out.  The  well  efficiency  represents  total  percentage  of  well 
water  used  for  irrigation.  Line  No.  5  represents  the  flow 
in  gallons  per  minute  of  the  well  to  produce  a  quantity  of  water 
available  for  irrigation  in  acre-feet  represented  by  line  6.  Line  7 
gives  the  percentage  of  increase  of  the  well  due  to  storage  of 
the  water  over  the  available  irrigation  water  without  a  reservoir. 
Line  8  gives  the  total  cost  of  water  for  irrigation  per  acre-foot 
representing  the  output  of  the  reservoir  and  the  flow  of  the 
well  on  the  ground  direct.  Line  9  gives  the  cost  of  the  reservoir 
per  acre-foot  of  water  used  for  irrigation,  as  defined. 

The  assumption  made  of  the  25  per  cent  irrigation  factor 
would  correspond  to  an  irrigation  season  about  four  months  in 
length,  the  total  flow  of  the  well  being  supposed  to  be  used 
three-fourths  of  that  time.  For  the  irrigation  of  a  crop  like 
cotton  in  Southern  Texas,  it  is  probable  that  the  irrigation  factor 
would  be  considerably  larger.  The  cost  of  water  without  a 
reservoir  in  the  cases  considered  would  be  $8  per  acre-foot  for 
Cases  A  and  C,  and  SI  for  Cases  B  and  D. 

The  method  of  interpretation  of  the  curves  given  in  these 
figures  is  similar  to  that  previously  given  on  page  169,  and  hence 
will  not  be  repeated.  In  Case  A-l,  as  given  in  Table  LI 


//-;    OF    Ah'TESIAN    WATER. 


193 


we  see  that  allowing  a  3-foot  clearance,  a  well  delivering  334 
gallons  per  minute  could  be  used  to  advantage  for  supplying  355 
acre-feet  per  year  by  means  of  a  reservoir  costing  $23.30  X  355. 
The  total  cost  of  the  water  for  irrigation  with  the  reservoir,  per 
acre-foot,  would  be  $5.51  as  against  $8  without  the  reservoir, 
and  the  reservoir  would  increase  the  quantity  of  water  actually 
used,  and  hence  the  land  which  could  be  irrigated  would  be 
increased  163  per  cent. 

Before  undertaking  any  reservoir  construction  based  on 
assumptions  which  have  been  made  here,  care  should  be  taken 
to  verify  these  assumptions  and  to  see  that  they  apply  to  the 
particular  case  considered.  It  is,  of  course,  evident  that  large 
reservoirs  like  those  described  will  increase  materially  the 
available  output  of  the  wells,  but  the  same  may  be  done  by  the 
use  of  pumps  assisting  the  artesian  flow. 

In  order  to  enable  one  to  pass  judgment  on  the  relative 
advantage  of  reservoirs,  or  of  the  use  of  pumps  for  increasing 
the  flow  of  wells,  it  would  be  necessary  to  have,  first,  an  under- 
standing of  the  law  of  the  flow  of  water  from  wells,  which  may 
be  arrived  at  as  outlined.  Generally  speaking,  pumps  may  be 
applied  to  increase  the  flow  of  the  wells  very  materially  when  the 
static  head  above  the  ground  is  small,  and  likewise  the  head  lost 
in  friction  in  flowing  through  the  pipes.  On  the  other  hand, 
where  the  static  head  is  large,  and  lost  friction  head  in  the  pipes 
is  also  large,  the  pumps  cannot  be  advantageously  employed. 

ECONOMIC   RESERVOIRS   FOR   ARTESIAN    WELLS. 

TABLE   LI. 

CASE  A-l. 

COST  PER  ACRE-FOOT   WELL  OUTPUT— $2. 


Diameter  of  reservoir,  ft.      .        400        800 

1200 

1600    2000   3000   4000 

Depth  of  embankment,  ft.    .   ;       6  .78    7  .93 

8.93 

9  .77  10  .58  12  .34  13  .85 

Reservoir  efficiency,  per  cent        30  .6 

42.3 

49.6 

54  .4    58  .2    64  .7    68  .9 

Well  efficiency,  per  cent   .    .  I     48  .0 

56.7 

59.7 

65.8 

68  .7    73  .5    76  .7 

Flow  of  well,  gal.  per  min.    . 

13.8 

66.3 

178 

334 

570 

1,520 

3,070 

Total  quantity  annually  use- 

ful for  irrigation,  acre-ft.  . 

10.7 

60.5 

171 

355 

&32  1,802  3,790 

Increase     over     what     well 

92      127 

149 

163 

175      194      207 

would  irrigate  without  res- 

ervoir, per  cent 

Total  cost  of  water  irrigation 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

with  reservoir,  per  acre-ft. 

14.66 

8.40 

6.49 

5.51 

4.90 

4.10 

3.68 

Cost  of  reservoir  per  acre-ft  . 

of  water  used  for  irrigation  .    102  .10  46  .70  31  .10  23  .30  18  .70  12  .80    9  .70 

194 


PRACTICAL  IRRIGATION. 


TABLE  LIT. 

CASE  A-2. 
COST  PER  ACRE-FOOT   OF  WELL  OUTPUT  — $2. 


Diameter  of  reservoir,  ft.    .    . 

400 

800 

1200 

1600 

2000 

3000 

4000 

Depth  of  embankment,  ft. 

7.09 

8.49 

9.66 

10.70 

11  .60 

13.78 

15.57 

Reservoir  efficiency,  per  cent 

34  .4 

46.6 

53.8 

58.8 

62.2 

68.7 

72.6 

Well  efficiency,  per  cent     .    . 

50.8 

60.0 

65.3 

69.1 

71.7 

76.5 

79.4 

Flow  of  well,  gal.  per  min.  . 

15.6 

71  .5 

186 

369 

631 

1,715 

3,470 

Total  quantity  annually  use- 

ful for  irrigation,  acre-ft.    . 

11.8 

69.0 

196 

412 

730 

2,115 

4,450 

Increase  over  what  well  would 

irrigate    without  reservoir, 

per  cent     

103 

140 

162 

177 

187 

206 

218 

Total  cost  of  water  for  irriga- 

tion   with    reservoir,    per 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

acre-ft    .    .        .... 

12.68 

7.46 

5.80 

4.95 

4.47 

3.77 

3  .42 

Cost  of  reservoir  per  acre-ft. 

of  water  used  for  irrigation 

84.80 

39.50 

26.00 

19.40 

15  .70 

10.70 

8.30 

TABLE   LIII. 

CASE  B-l. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT 


25  CENTS. 


Diameter  of  reservoir,  ft.    .    . 

400 

800 

1200 

1600 

2000 

3000 

4000 

Depth  of  embankment,  ft. 

5.76 

6.06 

6.35 

6.66 

6.95 

7.60 

8.20 

Reservoir  efficiency,  per  cent 

16.0 

20.9 

25.2 

29.3 

32.8 

39.4 

44.5 

Well  efficiency,  per  cent     .    . 
Flow  of  well,  gal.  per  min.     . 

37.0 
11  .4 

40.7 
48.1 

43.9 
115 

47.0 
217 

49.6 
355 

54  .6 

884 

58.3 
1,720 

Total  quantity  annually  use- 

ful for  irrigation,  acre-ft.    . 

6.8 

31.6 

81.5 

164 

284 

780 

1,613 

Increase  over  what  well  would 

irrigate   without   reservoir, 

per  cent  •    •    • 

48 

63 

76 

88 

98 

118 

134 

Total  cost  of  water  for  irriga- 

tion    with    reservoir,    per 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

acre-ft  

13  .03 

6  .51 

4.4 

3  .42 

2.78 

1  .96 

1  .57 

Cost  of  reservoir  per  acre-ft. 

of  water  used  for  irrigation 

119.00 

56.1 

35.77 

26.9 

20.1 

12.8 

9.5 

TABLE   LIV. 

CASE  B-2. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  —  25  CENTS. 


Diameter  of  reservoir,  ft.    .    . 

400 

800 

1200 

1600 

2000 

3000 

4000 

Depth  of  embankment,  ft.      . 

5.81 

6.21 

6.59 

6.92 

7.29 

8.09 

8.80 

Reservoir  efficiency,  ft.  .    .    . 
Well  efficiency,  per  cent     .    . 

16.8 
37.6 

23.2 
42.4 

29.0 
46.7 

32.4 
49.3 

36.5 
52.4 

43.3 
57.5 

48.7 
61  .5 

Rate  of  flow  of  well,  gal.  per 

min  

11  .5 

49.6 

119 

226 

374 

956 

1,860 

Total  quantity  annually  use- 

ful for  irrigation,  acre-ft.    . 

7.0 

34.0 

89.7 

179.7 

316 

885 

1,845 

Increase  over  what  well  would 

irrigate  without   reservoir, 

per  cent     .    .  '  

50 

70 

87 

97 

110 

130 

146 

Total  cost  of  water  for  irriga- 

tion   with    reservoir,    per 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

acre-ft  

11.14 

5.61 

3.79 

3.09 

2.39 

1.68 

1  .35 

Cost  of  reservoir  per  acre-ft. 

of  water  used  for  irrigation 

100.4 

46.6 

39.4 

23.1 

16.7 

10.5 

7.8 

STORAGE    OF   ARTESIAN    WATER. 


195 


TABLE   LV. 

CASE  C-l. 
COST  PER  ACRE-FOOT  OF   WELL  OUTPUT  — $2. 


Diameter  of  reservoir,  ft.    .    . 

400 

800 

1200 

1600 

2000    3000 

4000 

Depth  of  embankment,  ft.      . 

7.41 

8.73 

9.83 

10.7611  .62 

13.46 

15.15 

Reservoir  efficiency,  per  cent 

37.6 

48.3 

54.7 

59.0  |62.2 

67.8 

72.8 

Well  efficiency,  per  cent     .    . 

53.2 

61  .2 

66.0 

69.2 

71.7 

75.9 

78.8 

Flow  of  well,  gal.  per  min. 

15.2 

73.5 

189 

372 

633 

1,670 

3,620 

Total  quantity  annually  use- 

ful for  irrigation,  acre-ft.    . 

13.1 

72.8 

201.6 

416 

733 

2,045 

4,250 

Increase  over  what  well  would 

irrigate   without    reservoir, 

per  cent     

112 

145 

164 

177 

187 

203 

217 

Total  cost  of  water  for  irriga- 

tion    with    reservoir,     per 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

acre-ft 

9.94 

6.32 

5.12 

4.49 

4.11 

3.59 

3.29 

Cost  of  reservoir  per  acre-ft. 

of  water  used  for  irrigation 

59.5 

28.9 

19.5 

14.9 

12.2 

8.7 

6.8 

TABLE   LVI. 

CASE  C-2. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  — $2. 


Diameter  of  reservoir,  ft.    .    . 
Depth  of  embankment,  ft.     . 
Reservoir  efficiency,  per  cent 
Well  efficiency,  per  cent      .    . 
Flow  of  well,  gal.  per  min. 
Total  quantity  annually  use- 
ful for  irrigation,  acre-ft.    . 
Increase  over  what  well  would 
irrigate   without   reservoir, 
per  cent         

400 
7.84 
41.5 
56.1 
16.3 

14.7 
124 

800 
9.55 
53.2 
64.8 
81.5 

85.4 
160 

1200 
10.90 
59.6 
69.7 
210 

237 
179 

1600 
12.07 
63.8 

72.7 
423 

497 
191 

2000 
13.11 
66.9 
75.1 
723 

876 
201 

3000 
15.33 
72.1 
79.0 
1,928 

2,452 
217 

4000 
16.92 
75.0 
81.2 
3,800 

4,972 
225 

Total  cost  of  water  for  irriga- 
tion   with    reservoir,    per 
acre-ft 

Dolls. 
8  10 

Dolls. 
5  40 

Dolls. 
4  47 

Dolls. 
3  98 

Dolls. 
3  69 

Dolls. 
3  27 

Dolls. 

3  03 

Cost  of  reservoir  per  acre-ft. 
of  water  used  for  irrigation 

43.3 

21.7 

14.8 

11.4 

9.4 

6.7 

5.0 

TABLE   LVII. 

CASE  D-l. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  — 25  CENTS. 


Diameter  of  reservoir,  ft.    .    . 
Depth  of  embankment,  ft. 
Reservoir  efficiency,  per  cent 
Well  efficiency,  per  cent     .    . 
Flow  of  well,  gal.  per  min. 
Total  quantity  annually  use- 
ful for  irrigation,  acre-ft.    . 
Increase  over  what  well  would 
irrigate   without    reservoir, 
per  cent 

400 
6.10 
21.6 
41.2 
12.2 

8.1 
65 

800 
6.50 
27.3 
45.4 
52.3 

38.4 
82 

1200 
6.89 
32.2 
49.1 
126 

100 
96 

1600 
7.26 
36.1 
52.1 
238 

200 
108 

2000 
7.60 
39.4 
54.5 
393 

346 
118 

3000 
8.36 
45.7 
59.2 

988 

945 
137 

4000 
9.15 
50.9 
63.2 
1,945 

1,980 
152 

Total  cost  of  water  for  irriga- 
tion   with     reservoir,    per 
acre-ft                

Dolls. 

7.75 

Dolls. 

4.06 

Dolls. 
2.33 

Dolls. 
2  21 

I)  i 
1  .86 

Dolls. 

1  38 

Dolls. 

1  13 

Cost  of  reservoir  per  acre-ft. 
of  water  used  for  irrigation 

67.7 

31  .9 

20.5 

14.9 

11.8 

7.8 

5.8 

196 


PRACTICAL  IRRIGATION. 


TABLE  LVIII. 

CASE  D-2. 
COST  PER  ACRE-FOOT  OF  WELL   OUTPUT  — 25   CENTS. 


Diameter  of  reservoir,  ft.    .    . 

400 

800 

1200 

1600 

2000 

3000 

4000 

Depth  of  embankment,  ft.     . 

6.11 

6.70 

7.21 

7.68 

8.12 

9.08 

9.92 

Reservoir  efficiency,  per  cent 

21.7 

29.8 

35.6 

40.1 

43.8 

50.5 

55.1 

Well  efficiency,  per  cent     .    . 
Flow  of  well,  gal.  per  min.     . 

41  .3 
42.2 

47.4 
53.5 

51.7 
121 

55.4 
255 

57.9 
425 

62.9 
1,090 

66.3 
2,135 

Total  quantity  annually  use- 

ful for  irrigation,  acre-ft.    . 

8.1 

40.9 

101  .3 

226.7 

396.0 

1,105 

2,280 

Increase  over  what  well  would 

irrigate  without   reservoir, 

per  cent         .        

65 

89 

107 

120 

131 

152 

166 

Total  cost  of  water  for  irriga- 

tion   with    reservoir,    per 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

Dolls. 

acre-ft  

6.08 

3.20 

2  .20    1  .78 

1.49 

1.12 

.94 

Cost  of  reservoir  per  acre-ft. 

of  water  used  for  irrigation 

51  .0 

23.8 

15.7 

11  .1 

8.7 

5.7 

4.3 

TABLE   LIX. 

CASE  E-l. 
COST  PER  ACRE-FOOT  OF  WELL   OUTPUT  — $2. 


Diameter  of  reservoir,  ft     

400 

600 

800 

1000 

1200 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent 
Well  efficiency,  per  cent     
Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 
irrigation,  acre-ft                  .    . 

5.39 

25.8 
44  .4 
12.8 

9.2 

6.06 
34.0 
50.5 
32.5 

26.4 

6.72 
40.5 
55.4 
64.0 

57.1 

7.21 
44.5 

58.4 
107.5 

101  .2 

7.72 
48.2 
61.1 
166.0 

163.5 

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total   cost   of   water   for  irrigation 
with  reservoir,  per  acre-ft.     .    .    . 
Cost    of    reservoir    per    acre-ft.     of 
water  used  for  irrigation  .... 

77 

Dolls. 
12  .56 

77.20 

102 

Dolls. 
9.25 

40.30 

121 

Dolls. 

7.56 
37.30 

133 

Dolls. 
6.63 

30.10 

145 

Dolls. 
5.95 

25  .10 

TABLE  LX. 

CASE  E-2. 

COST  PER  ACRE-FOOT    OF   WELL  OUTPUT  — $2. 


Diameter  of  reservoir  ft             ... 

400 

600 

800 

1000 

1200 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent     .    .    . 
Well  efficiency,  per  cent     

5.76 
30.6 
47.9 

6.55 
39.0 
54.2 

7.25 

44.8 
58.7 

7.91 
49.4 
62.1 

8.50 
53.0 
64.7 

Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 
irrigation,  acre-ft                     .    . 

13.7 
10.6 

35.2 
30.7 

69.2 
65.5 

117.5 
117.5 

182.0 
190.2 

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total  cost  of  water  for  irrigation  with 
reservoir,  per  ft  
Cost  of  reservoir  per  acre-ft.  of  water 
used  for  irrigation    

92 

Dolls. 
10.96 

65  .00 

117 

Dolls. 

8.20 
42.80 

134 

Dolls. 
6.79 

31  .90 

148 

Dolls. 
5.98 

25  .60 

159 

Dolls. 
5.40 

21.60 

STORAGE    OF   ARTESIAN    WATER. 


197 


TABLE  LXI. 

CASE  F-l. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  — 25  CENTS. 


Diameter  of  reservoir,  ft  

400 

600 

800 

1000 

1200 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent    .    .    . 

4.16 
3.8 
27.9 

4.36 
8.3 
31  .2 

4.56 
12.3 
33.5 

4.74 
15.6 
36.7 

5.06 
20.9 
40.7 

Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 

9.8 
4.44 

23.3 
11.74 

44.3 
24.00 

71.0 
42.10 

109.0 
71.50 

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total  cost  of  water  for  irrigation  with 

11 

Dolls. 
10.80 

25 

Dolls. 
7.22 

37 

Dolls. 
5.44 

47 

Dolls. 
4.40 

63 

Dolls. 
3.64 

Cost  of  reservoir  per  acre-ft.  of  water 
used  for  irrigation    

92.20 

58.30 

42.00 

32.70 

26.40 

TABLE  LXII. 

CASE  F-2. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  — 25  CENTS. 


Diameter  of  reservoir  ft 

400 
4.31 
7.2 
30.4 
10.3 

5.03 
22 

Dolls. 

8.98 
75.50 

600 
4.55 
12.1 
34.0 

24.8 

13.35 
36 

Dolls. 
6.07 

58.20 

800 
4.77 
16.2 
37.1 
45.7 

27.30 
49 

Dolls. 
4.61 

34.90 

1000 
5.00 
20.0 
40.0 
74.1 

47.90 
60 

Dolls. 

3.74 

27.20 

1200 
5.20 
23.1 
42.3 
112.0 

76.30 
69 

Dolls. 
3.19 

22  .40 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent     .    .    . 
Well  efficiency  per  cent     .        ... 

Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 
irrigation,  acre-ft  

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total  cost  of  water  for  irrigation  with 
reservoir,  per  acre-ft    

Cost  of  reservoir  per  acre-ft.  of  water 
used  for  irrigation    

TABLE   LXIII. 

CASE  G-l. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  — $2. 


Diameter  of  reservoir  ft 

400 
6.27 
36.2 
52.2 
14.0 

12.56 
109 

Dolls. 
8.65 

45  .70 

600 
7.00 
42.8 
57.2 
37.5 

34.70 
128 

Dolls. 
6.74 

30.40 

800 
7.68 
47.9 
61  .0 
73.2 

72.00 
143 

Dolls. 
5.76 

23  .10 

1000 
8.27 
51.7 
63.8 
123.4 

126  .80 
155 

Dolls. 
5.15 

18.60 

1200 
8.82 
54.7 
66.0 
190.0 

201  .60 
164 

Dolls. 

4.78 
15.10 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent     .    .    . 
Well  efficiency,  per  cent     
Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 
irrigation   acre-ft 

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total  cost  of  water  for  irrigation  with 

Cost  of  reservoir  per  acre-ft.  of  water 
used  for  irrigation    

198 


PRACTICAL  IRRIGATION. 


TABLE   LXIV. 

CASE  G-2. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  — $2. 


Diameter  of  reservoir  ft 

400 

600 

800 

1000 

1200 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent     .    .    . 
Well  efficiency,  per  cent     .    . 

6.96 
42.5 
57.0 

7.89 
49.4 
62.0 

8.70 
54.1 
65.5 

9.37 
57.3 
68.0 

10.08 
60.3 
70.3 

Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 
irrigation,  acre-ft  

16.5 
15.24 

42.3 
42.30 

88.0 
87.80 

150.0 
153.0 

216.0 
245.0 

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total  cost  of  water  for  irrigation  with 
reservoir,  per  acre-ft  
Cost  of  reservoir  per  acre-ft.  of  water 
used  for  irrigation    

127 

Dolls. 

7.67 
34.50 

148 
Dolls. 

5.71 
23.20 

162 

Dolls. 
4.97 

17.80 

172 

Dolls. 
4.52 

14.50 

181 

Dolls. 
4.20 

12.40 

TABLE  LXV. 

CASE  H-l. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  —  25  CENTS. 


Diameter  of  reservoir,  ft  

400 

600 

800 

1000 

1200 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent     .    .    . 
Well  efficiency,  per  cent 

4.68 
14.5 
35  9 

4.95 
19.2 
39.4 

5.21 
23.8 
42.9 

5.45 
26.6 
45  .5 

5.67 
29.5 
47.1 

Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 
irrigation,  acre-ft  

11  .2 
6.4 

26.5 
16.9 

49.2 
34.0 

80.2 
58  9 

122.0 
92.5 

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total  cost  of  water  for  irrigation  with 
reservoir,  per  acre-ft  
Cost  of  reservoir  per  acre-ft.  of  water 
used  for  irrigation    

43 

Dolls. 

6.48 
53.1 

57 

Dolls. 

4.40 
33.60 

71 

Dolls. 
3.39 

24.40 

80 

Dolls. 
2.78 

19.00 

88 

Dolls. 
2.39 

15.60 

TABLE  LXVI. 

CASE  H-2. 
COST  PER  ACRE-FOOT  OF  WELL  OUTPUT  — $2. 


400 

600 

800 

1000 

1200 

Depth  of  embankment,  ft  
Reservoir  efficiency,  per  cent     .    .    . 
Well  efficiency  per  cent 

5.09 
21  .4 
41   1 

5.43 
26.4 

44  8 

5.73 
30.2 
47  .6 

6.01 
33.5 
50  .1 

6.29 
36.5 
52.3 

Flow  of  well,  gal.  per  min  
Total  quantity  annually  useful  for 
irrigation,  acre-ft         ...        .    . 

12.2 
8.1 

29.1 
21  .0 

54.8 
42.0 

89.8 
72.5 

135.0 
113.8 

Increase  over  what  well  would  irri- 
gate without  reservoir,  per  cent 
Total  cost  of  water  for  irrigation  with 
reservoir,  per  acre-ft        .... 

64 

Dolls. 

3  78 

79 

Dolls. 
3  .32 

91 

Dolls. 
2.59 

100 

Dolls. 
2.15 

109 

Dolls. 

1.87 

Cost  of  reservoir  per  acre-ft.  of  water 
used  for  irrigation    

38.00 

24  .30 

17.80 

13  .90 

11.50 

CHAPTER   XVI. 

ECONOMICS  USES  OF  RESERVOIRS  AND  TANKS. 

IN  case  it  is  desired  to  irrigate  only  during  the  daytime,  and 
not  at  night,  then  provided  a  reservoir  is  constructed  to  hold  the 
night  supply  of  the  pump,  a  far  smaller  pump  plant  may  be 
installed  to  perform  the  same  work  required  of  a  plant  operated 
only  during  the  daytime.  The  cost  of  a  reservoir  will  generally 
be  much  less  than  the  cost  of  doubling  the  size  of  the  pump  plant. 
The  smaller  plant  will,  in  general,  require  more  fuel  for  the 
delivery  of  a  given  quantity  of  water,  owing  to  the  lower  effi- 
ciency of  smaller  units,  and  will  also  need  more  labor;  but,  on  the 
other  hand,  the  fixed  expenses  of  the  smaller  plant  will  be  much 
less.  In  case  the  plant  is  used  only  a  comparatively  short  time 
during  the  year,  for  irrigation,  usually  the  fixed  expenses  will 
be  far  in  excess  of  the  operating  expenses,  and  it  will  pay  to  put 
in  the  smaller  plant  and  reservoir,  especially  where  labor  is 
cheap.  To  get  up  steam  in  plants  which  run  only  in  the  day- 
time will  require  an  amount  of  fuel  equal  to  that  consumed  in 
from  1  to  2  hours'  full-load  run. 

In  plants  pumping  from  wells  where  a  great  part  of  the  head 
consists  of  the  distance  the  water  is  lowered  in  the  well,  a  very 
large  fuel  saving  may  be  made  by  operating  a  small  plant  a  long 
time  rather  than  a  large  plant  a  shorter  time. 

Existing  plants,  where  night  irrigation  is  undesirable,  may 
have  their  capacity  greatly  increased  by  the  construction  of 
reservoirs  to  hold  the  night  supply  of  the  pump.  The  cost  of 
such  reservoirs  is  usually  only  a  small  fraction  of  the  cost  of  the 
pumping  plants  which  will  supply  them.  It  is  frequently  desir- 
able not  to  irrigate  during  the  heat  of  the  day,  in  which  event  a 
reservoir  is  a  most  useful  aid  in  irrigation. 

To  illustrate  some  of  the  advantages  of  reservoirs  in  diminish- 
ing the  cost  of  irrigation,  some  examples  in  practice  will  be 
given  where  conditions  could  have  been  improved.  A  steam 
plant,  which  cost  $3,000,  was  used  to  pump  from  a  well.  The 

199 


200  PRACTICAL  IRRIGATION. 

plant  was  operated  10  hours  per  day.  The  quantity  of  water 
delivered  was  2,500  gal.  per  min.  and  the  head  50  feet. 
Water  stood  2  feet  below  the  ground  without  flow,  and  the 
friction  in  the  well  casing  and  piping  was  practically  the  only 
source  of  loss  of  head.  If  10  hours'  run  was  sufficient  for  the 
needs  of  the  land,  then  the  capacity  of  the  plant  could  have  been 

reduced  to  1040  gal.  per  min.,  if  run  for  24  hours.     Under  these 

/  1  \2 
conditions  the  lift  would  be  48  X   ( —    =  8.3  +  2  =  10.3  feet. 


Assuming  that  a  reservoir  is  built  to  hold  14  hours7  supply, 
say  that  the  additional  head  against  which  it  is  necessary  to 
pump  is,  on  an  average,  3.7  feet,  making  a  total  of  14  feet.  Then 
water  horsepower  at  present  =  31.6,  and  the  water  horsepower 
of  proposed  plant  =  3.67. 

In  the  first  case,  the  cost  of  operation  is 

$6. 30  per  day  for  fuel 
1 . 00  per  day  for  labor 
7.30  per  day, 

allowing  for  2  hours'  fuel  in  getting  up  steam.  The  cost  of  fuel 
for  power  for  the  new  plant  would  be  $1.46  per  day  at  the  same 
efficiency,  but  from  decreased  size  of  plant  would  be,  say, 

$3. 00  fuel 
2.00  labor 
5XJO         Daily  saving  $2.30. 

To  retain  1040  gal.  per  min.  for  14  hours  is  equivalent  to  608 
gal.  per  min.  for  24  hours,  or  to  2.7  acre-feet  capacity. 

As  the  ground  is  suitable  for  reservoir  construction,  assume 
that  an  earth  reservoir  of  3  acre-feet  capacity  is  built,  costing 
10  cents  per  cubic  yard.  By  Fig.  36,  Case  1,  we  can  make  this 
5  feet  deep  and  208  feet  diameter,  at  a  cost  of  $220,  or  6  feet  deep 
and  177  feet  in  diameter,  costing  $280;  and,  of  course,  at  con- 
siderably less  first  cost  if  we  adopt  the  slopes  of  Case  2.  Allowing 
$300  for  reservoir  and  land,  and  $1000  for  the  pump  plant,  makes 
a  saving  of  $1700  in  the  first  cost,  or  $340  a  year,  figuring  20  per 
cent  fixed  expenses  and  $2.30  a  day  in  operating  expenses.  In 
addition  to  a  saving  of  this  nature,  there  would  be  many  obvious 
advantages  from  a  reservoir,  in  the  better  regulation  of  the 


s-  or  /,'/•:>/•:  AM  'OIRS  AND  TANKS.  201 


quantity  of  water  needed,  and  in  operating  the  plant  at  its 
highest  efficiency.  The  present  plant  can  have  its  irrigation 
efficiency  materially  improved  by  the  addition  of  a  small  reser- 
voir, and  can  also  greatly  increase  its  available  limit  of  irrigation 
without  night  irrigation.  It  could  be  made  to  operate  more 
cheaply  by  running  longer  hours,  and  not  pumping  against  such 
a  high  head.  For  example,  by  operating  at  about  30  per  cent 
less  speed  for  40  per  cent  more  time,  the  same  quantity  of  water 
could  be  delivered  for  about  half  the  total  fuel  expenditure, 
provided  the  efficiency  were  the  same.  Practically,  the  efficiency 
would  diminish,  owing  to  the  engine  and  boiler  being  operated 
below  capacity,  but  still  considerable  fuel  saving  could  be 
expected  over  the  present  method  of  operation. 

If  it  were  desired  to  have  the  present  plant  irrigate  twice  the 
area  of  land  without  night  irrigation,  what  would  it  cost  to 
construct  a  reservoir,  and  what  dimensions  should  it  be  given? 
Let  cost  =  10  cents  per  cubic  yard.  To  store  2500  gal.  per  min. 
for  12  hours,  requires  5.5  acre-feet.  In  Case  1,  a  5-acre-foot 
reservoir,  5  feet  deep,  272  feet  in  diameter,  would  cost  $290; 
7  feet  deep  and  208  feet  diameter,  $440. 

A  certain  pump  plant  cost  $1250  for  the  pump  and  power 
station,  and  $1400  for  a  pipe  line.  The  capacity  of  the  pump  was 
800  gal.  per  min.,  and  the  cost  of  labor  55  cents  per  day.  The 
pump  operated  against  a  lift  of  65  feet  plus  friction  head,  and  12 
hours  per  day  were  sufficient  for  irrigation.  What  saving  could 
have  been  effected  if  the  pump  discharged  into  a  reservoir,  and 
operated  for  24  hours  a  day,  against  the  same  head?  If  a  plant 
of  half  the  capacity  were  installed  to  operate  continuously,  the 
first  cost  would  be  materially  lessened  as  indicated  below.  The 
present  plant  operates  for  45  days  a  year,  on  an  average. 

Present  cost  of  labor  per  day    .......         $0.55 

Present  cost  of  fuel  per  day     .......  5.00 

$5.55 

Annual  fuel  expense  =  45  X  5.00    .    .    .    .  $225 

Annual  labor  expense  =  45  X  0  .  55    ....  25 

Fixed  expense,  20  per  cent  on  $1250      .    .    .  250 

Fixed  expense,  12  per  cent  on  $1400      .    .    .  168 

Total  annual  expense     ........  $668 


202  PRACTICAL  IRRIGATION. 

If  a  reservoir  be  installed  to  hold  12  hours'  supply  of  a  plant  of 
half  this  capacity,  it  will  need  to  hold  200  gal.  per  min.  for  a  day, 
or  0.88  acre-feet.  The  soil  is  unsuitable  for  reservoir  construc- 
tion without  lining.  As  labor  is  very  cheap,  assume  the  reser- 
voir lined  with  puddle,  and  the  cost  of  labor  and  materials  is 
two-thirds  of  the  cost  assumed  in  Case  3L  Then  the  reservoir 
will  cost,  approximately,  $300. 

Allowing  for  increased  fuel  expense,  but  also  for  the  gain  from 
constant  operation, 

Cost  of  labor  per  day $1.10 

Cost  of  fuel  per  day 5 . 50 

$6.60 

Cost  of  power  house 700 

Cost  of  pipe  line 900 

Annual  fuel  expense  45  X  5.5  .  .  .  .  $250 
Annual  labor  expense  45  X  1.10  .  .  50 
Fixed  expense,  20  per  cent,  $700  for 

power  plant 140 

Fixed  expense,  12  per  cent,  $900  for 

pipe  line 72 

Fixed  expense,  12  per  cent,  $300  for 

reservoir 36 

Total ~  $548 

$668 
548 
Saving  per  year $120 


APPENDIX  A. 

TABLE   LXVII. 
LIST  OF  RESERVOIR  CASES  AND  ASSUMED  DATA. 


Cases 

Quantities 

B. 

C. 

w. 

b. 

9- 

/. 

w. 

p. 

s. 

T. 

la 

6.00 

2.00 

4.00 

3.00 

4.00 

.25 

5.00 

2.00 

3.00 

2.50 

16      .    . 

6.0 

2.0 

4.0 

3.0 

4  .0 

2.0 

30.0 

2.0 

3.0 

2.5 

lc      .    . 

8.00 

4.00 

10.00 

5.00 

4.00 

.25 

5.00 

2.00 

3  .00    2  .50 

Id     .    . 

6.00 

2.00 

4  .00 

3.00 

4.00 

.25 

5.00 

2  .00    3  .00    2  .50 

le      .    . 

8.00 

4.00 

10.00 

5.00 

4.00 

.25 

5.00 

2.00    3.00    2.50 

2a     .    . 

6.00 

2.00 

4.00 

3.00 

4.00 

.25 

5.00 

1  .50    2  .00    1  .75 

26     .    . 

6.00 

2.00 

4.00 

3.00 

4.00 

2.00 

30.00 

1  .50    2  .00    1  .75 

If     .    . 

6.00 

2.00 

4.00 

3  .00 

4.00 

.25 

5.00 

2.00 

3.00 

2.50 

10     •    • 

6.00 

2.00 

4.00 

3  .00 

4.00 

2.00 

30.00 

2.00 

3.00 

2.50 

Ih    .    . 

8.00 

4.00 

10.00 

5.00 

4  .00 

.25 

5.00 

2.00    3.00 

2.50 

It     .    . 

6.00 

2.00 

4.00 

3.00 

4.00 

2.00 

30.00 

2.00    3.00 

2.50 

3fc    .    . 

5.00 

2.00 

4.00 

3.00    4.00 

2.00 

30  .00    1  .50    1  .50 

1.50 

3Z     .    . 

1.00 

1.00 

4.00 

1  .00 

0.00 

30  .00    1  .50    1  .50 

1.50 

3w  .    . 

2.00 

2.00 

4.00 

2.00 

0.00 

30  .00    1  .50 

1.50 

1  .50 

laa  .    . 

6.00 

2.00 

4.00 

3.00 

4.00 

.25 

5.00   2.00 

3.00 

2.50 

4a    .    . 

6.00 

2.00 

* 

3.00 

4.00 

.25 

5.00 

2.10 

2.61 

2.36 

fAl    .    . 

5.0 

1  .0 

4.0 

3.0 

3.0 

2.0 

15.0 

2.0 

3.0 

2.5 

A2   .    . 

5.00 

.00 

4.00 

3.00 

3.00 

2.00 

15.00 

1.50 

2.00 

1.75 

Bl    .    . 

5.00 

.00    4.00 

3.00 

3.00 

.25 

15.00 

2.00 

3.00 

2.50 

E 

B2   .    . 

5.00 

.00 

4.00 

3.00 

3.00 

.25 

15.00 

1  .50 

2.00 

1.75 

5 

Cl     .    . 

5.0 

.0 

4.0 

3.0 

3.0 

2.0 

15.0 

2.0 

3.0 

2.5 

# 

C2    .    . 

5.00 

.00 

4.00 

3.00 

3.00 

2.00 

15.00 

1.50 

2.00 

1.75 

£ 

Dl    .    . 

5.00 

.00 

4.00 

3  .00 

3.00 

.25 

15.00 

2.00 

3.00 

2.50 

«—  •  • 

D2  .    . 

5.00 

.00 

4  .00 

3  .00 

3.00 

.25 

15.00 

1.50 

2.00 

1.75 

~v 

C 

El    .    . 

4.00 

0.00 

4  .00 

2.00 

3.00 

2.00 

15.00 

2.00 

3.00 

2.50 

|F 

E2  .    . 

4.00 

0.00 

4.00 

2.00 

3.00 

2.00 

15.00 

1.50 

2.00 

1.75 

c 

.2 

Fl    .    . 

4.00 

0.00 

4.00 

2.00 

3.00 

.25 

15.00 

2.00 

3.00 

2.50 

S 

F2   .    . 

4.00 

0.00 

4.00 

2.00 

3.00 

.25 

15.00 

1  .50 

2.00 

1.75 

« 

Gl    .    . 

4.00 

0.00 

4.00 

2.00 

3.00 

2.00 

15.00 

2.00 

3.00 

2.50 

•< 

G2    .    . 

4.00 

0.00 

4.00 

2.00 

3.00 

2.00 

15.00 

1.50 

2.00 

1.75 

HI   .    . 

4.00 

0.00 

4.00 

2.00 

3.00 

.25 

15.00 

2.00 

3.00 

2.50 

LH2  .    . 

4.00 

0.00 

4.00 

2.00 

3.00 

.25 

15.00 

1  .50 

2.00 

1.70 

*W  =  H  +  5  -2bT=  #-9.13. 

If  H  =  9.13,  the  bank  would  have  no  crown.    This  applies  strictly  to  cases 
of  greater  values  of  H. 


203 


204 


PRACTICAL  IRRIGATION. 


TABLE   LXVII—  Concluded. 


Cases 

Quantities 

c. 

M. 

n. 

P' 

9w. 

t. 

d. 

i. 

k. 

<l> 

lOOOa 

la 
lb 
Ic 
Id 
le 
2a 
2b 
I/ 
10 
Ih 
li 
3k 
31 
3m 
laa 
4a 
Al 
A2 
Bl 
B2 
Cl 
C2 
Dl 
D2 
El 
E2 
Fl 
F2 
Gl 
G2 
HI 
H2 

6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
5.00 

.03 
.03 
.03 
.03 
.03 
.03 
.03 
.10 
.10 
.10 
.10 

.10 
.10 
.10 
.10 
.10 
.10 
.10 
.25 
.25 
0.22 
0.20 
.20 
0.15 

.10 
.10 
.10 
.10 
.10 
.10 
.10 
.12 
.12 
0.12 
0.10 
.10 

2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 

.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 

1  .00 
1.00 
1.00 
1  .00 
1  .00 
1.00 
1  .00 
1.00 
1  .00 
1  .00 
1.00 
1.00 

5.0 
5.0 
3.0 
5.0 
3.0 
5.0 
5.0 

0 
0 
0 

1 
1 

0 
0 
2 
2 
2 
2 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 

6  '.is 

0.90 
0  18 

12.00 
12.00 
12.00 
12.00 

6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 
6.00 

.03 
.03 
.03 
.03 
.03 
.03 

.15 
.10 
.10 
.10 
.10 
.10 
.10 
.10 
.10 

!io 

.10 
.10 
.10 
.10 
.10 
.10 
.10 

0.18 

2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 
2.00 

.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 
.07 

1.00 
1  .00 
1  .00 
1  .00 
1.00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 
1  .00 

3.0 
5.0 
3.0 
3.0 
3.0 
3.0 

3  '.6 
3.0 
3.0 
3.0 

— 

— 

.03 
.03 
.03 
.03 

.10 
.10 
.10 
.10 
.10 
.10 
.10 
.10 
.10 
.10 

.10 
.10 
.10 
.10 
.10 
.10 
.10 
.10 
.10 
.10 

.... 

— 

.... 

B 

W 


b  +  g  -  k. 

width  of  crown  of  bank. 


b  =  clearance. 

g  =  depth  of  evaporation  and  seep- 

age  losses  during  irrigation 

season. 
I  =  $  cost  per  acre-foot  of  water 

delivered  to  reservoir. 
v  =  $  cost  of  land  per  acre. 
P  —  I  -i-  slope  of  outside  bank. 
S  =  l-:-  slope  of  inside  bank. 

r-i(p  +  s). 

c  =  depth   in   reservoir  of  annual 
evaporation  and  seepage. 


?7i    =  $  cost  of  riprap  per  sq.  ft. 

n     —  $  cost  of  embankment  construc- 
tion per  cu.  yd. 

p     =  per  cent  annual  interest,  main- 
tenance   and    depreciation    of 
reservoir, 
cost  of  puddle  per  sq.  yd. 


Qw 
t 
d 
i 


=  width  of  riprap. 

=  annual  rainfall. 

=  per  cent,  interest  charges. 
k    =  depth  of  water  applied  to  reser- 
voir during  irrigation  season. 
q    =  constant. 
a    =  ground  slope. 


NOTE.  In  cases  A2,  B2,  E2  and  F2,  the  width  of  riprap  is  taken  as 
3  (H  -  q)  =  3  (H  -  3).  This  applies  in  Case  2,  when  H  <  12'.  If  H  =  12 
the  entire  bank  would  be  riprapped.  A  greater  value  of  H  would  mean  a 
quantity  of  riprap  in  excess  of  the  length  of  bank. 


APPENDIX   A. 


205 


TABLE  LXVIII. 
CONE    RESERVOIRS. 


Side  Slopes 


1  ft.  vertical  to  3  ft. 

1  ft.  vertical  to  2  ft. 

1  ft.  vertical  to  1.5  ft. 

horizontal 

horizontal 

horizontal 

I 
£ 

Diam- 
eter 

Capacity 
for  pre- 
ceding 
1  ft.  of 

Total 
capacity 
for  cor- 
respond- 

Diam- 
eter 

Capacity 
for  pre- 
ceding 
1  ft.  of 

Total 
capacity 
for  cor- 
respond- 

Diam- 
eter 

Capacity 
for  pre- 
ceding 
1  ft.  of 

Total 
capacity 
for  cor- 
respond- 

depth 

ing  depth 

depth 

ing  depth 

depth 

ing  depth 

Ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

1 

6 

.000 

.000 

4 

.000 

.000 

3 

.000 

.000 

2 

12 

.002 

.002 

8 

.001 

.001 

6 

.000 

.000 

3 

18 

.004 

.006 

12 

.002 

.003 

9 

.001 

.001 

4 

24 

.008 

.014 

16 

..004 

.007 

12 

.002 

.003 

5 

30 

.013 

.027 

20 

.006 

.013 

15 

.003 

.006 

6 

36 

.020 

.047 

24 

.009 

.022 

18 

.005 

.011 

7 

42 

.027 

.074 

28 

.012 

.034 

21 

.007 

.018 

8 

48 

.037 

.111 

32 

.016 

.050 

24 

.009 

.027 

9 

54 

.047 

.158 

36 

.021 

.071 

27 

.012 

.039 

10 

60 

.059 

.217 

40 

.026 

.097 

30 

.015 

.054 

11 

66 

.072 

.289 

44 

.032 

.129 

33 

.018 

.072 

12 

72 

.086 

.375 

48 

.038 

.167 

36 

.021 

.093 

13 

78 

.101 

.476 

52 

.045 

.212 

39 

.025 

.118 

14 

84 

.118 

.594 

56 

.052 

.264 

42 

.030 

.148 

15 

90 

.136 

.730 

60 

.061 

.325 

45 

.034 

.182 

16 

96 

.156 

.886 

64 

.069 

.394 

48 

.039 

.221 

17 

102 

.177 

1  .063 

68 

.079 

.473 

51 

.044 

.265 

18 

108 

.199 

1.262 

72 

.088 

.561 

54 

.050 

.315 

19 

114 

.222 

1.484 

76 

.099 

.660 

57 

.055 

.370 

20 

120 

.247 

1.731 

80 

.110 

.770 

60 

.062 

.432 

21 

126 

.272 

2.003 

84 

.121 

.891 

63 

.068 

.500 

22 

132 

.300 

2.303 

88 

.133 

1.024 

66 

.075 

.575 

23 

138 

.328 

2.631 

92 

.146 

1.170 

69 

.082 

.657 

24 

144 

.358 

2.989 

96 

.159 

1  .329 

72 

.089 

.746 

25 

150 

.389 

3  .378 

100 

.173 

1.502 

75 

.097 

.843 

26 

156 

.422 

3.800 

104 

.187 

1.689 

78 

.105 

.948 

27 

162 

.455 

4.255 

108 

.202 

1.891 

81 

.114 

1.062 

28 

168 

.490 

4.745 

112 

.218 

2.109 

84 

.122 

1.184 

29 

174 

.526 

5.271 

116 

.234 

2.343 

87 

.132 

1.316 

30 

180 

.564 

5.835 

120 

.251 

2.594 

90 

.141 

1.457 

31 

186 

.603 

6.438 

124 

.268 

2.862 

93 

.151 

1  .608 

32 

192 

.643 

7.081 

128 

.286 

3.148 

96 

.161 

1.769 

33 

198 

.685 

7.766 

132 

.305 

3.453 

99 

.171 

1.940 

34 

204 

.728 

8.494 

136 

.323 

3.776 

102 

.182 

2.122 

35 

210 

.772 

9.266 

140 

.343 

4.119 

105 

.193 

2.315 

36 

216 

.817 

10  .083 

144 

.363 

4.482 

108 

.204 

2  .519 

37 

222 

.864 

10  .947 

148 

.384 

4.866 

111 

.216 

2.735 

38 

228 

.912 

11  .859 

152 

.405 

5.271 

114 

.228 

2.963 

39 

234 

.961 

12  .820 

156 

.427 

5.698 

117 

.240 

3.203 

40 

240 

1.011 

13.831 

160 

.450 

6.148 

120 

.253 

3.456 

41 

246 

1  .064 

14  .895 

164 

.473 

6.621 

123 

.266 

3.722 

42 

252 

1  .116 

16.011 

168 

.496 

7.117 

126 

.279 

4.001 

206 


PRACTICAL  IRRIGATION. 
TABLE    LXVIII  —  Continued. 


Side  Slopes 


1  ft.  vertical  to  3  ft. 

1  ft.  vertical  to  2  ft. 

1  ft.  vertical  to  1.5  ft. 

horizontal 

horizontal 

horizontal 

1 

Capacity 

Total 

Capacity 

Total 

Capacity 

Total 

w 

Diam- 
eter 

for  pre- 
ceding 
1  ft.  of 

capacity 
for  cor- 
respond- 

Diam- 
eter 

for  pre- 
ceding 
1  ft.  of 

capacity 
for  cor- 
respond- 

Diam- 
eter 

for  pre- 
ceding 
1  ft.  of 

capacity 
for  cor- 
respond- 

depth 

ing  depth 

depth 

ing  depth 

depth 

ing  depth 

Ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

43 

258 

1.170 

17  .181 

172 

.521 

7.638 

129 

.293 

4.294 

44 

264 

1  .226 

18  .407 

176 

.545 

8.183 

132 

.307 

4.601 

45 

270 

1  .283 

19  .690 

180 

.570 

8.753 

135 

.321 

4.922 

46 

276 

.342 

21  .032 

184 

.597 

9.350 

138 

.335 

5.257 

47 

282 

.400 

22  .432 

188 

.623 

9.973 

141 

.350 

5.607 

48 

288 

.462 

23  .894 

192 

.650 

10  .623 

144 

.366 

5.973 

49 

294 

.525 

25  .419 

196 

.678 

11  .301 

147 

.381 

6.354 

50 

300 

.590 

27  .009 

200 

.707 

12  .008 

150 

.397 

6.751 

51 

306 

.655 

28  .664 

204 

.736 

12  .744 

153 

.413 

7.164 

52 

312 

.720 

30  .384 

208 

.764 

13  .508 

156 

.430 

7.594 

53 

318 

.787 

32  .171 

212 

.794 

14  .302 

159 

.447 

8.041 

54 

324 

1.856 

34  .027 

216 

.825 

15  .127 

162 

.463 

8.504 

55 

330 

1.925 

35  .952 

220 

.856 

15  .983 

165 

.481 

8.985 

56 

336 

1.996 

37  .948 

224 

.887 

16  .870 

168 

.498 

9.483 

57 

342 

2.070 

40  .018 

228 

.920 

17  .790 

171 

.517 

10  .000 

58 

348 

2.140 

42  .150 

232 

.952 

18  .742 

174 

.536 

10  .536 

59 

354 

2  .220 

44  .370 

236 

.986 

19  .728 

177 

.555 

11  .091 

60 

330 

2.300 

46  .670 

240 

1  .020 

20  .748 

180 

.573 

11  .664 

61 

366 

2.380 

49  .050 

244 

1  .054 

21  .802 

183 

.593 

12  .257 

62 

372 

2.450 

51  .500 

248 

1  .089 

22  .891 

186 

.613 

12  .870 

63 

378 

2.530 

54  .030 

252 

1.125 

24  .016 

189 

.633 

13  .503 

64 

384 

2.610 

56  .640 

256 

1.160 

25  .176 

192 

.652 

14  .155 

65 

390 

2.700 

59  .340 

260 

1.198 

26  .374 

195 

.674 

14  .829 

66 

396 

2.780 

62  .120 

264 

1  .234 

27  .608 

198 

.695 

15  .524 

67 

402 

2.870 

64  .990 

268 

1  .270 

28  .878 

201 

.716 

16  .240 

68 

408 

2.950 

67  .940 

272 

1  .313 

30  .191 

204 

.738 

16  .978 

69 

414 

3.040 

70  .980 

276 

1.351 

31  .542 

207 

.770 

17  .748 

70 

420 

3.130 

74  .110 

280 

1.390 

32  .932 

210 

.783 

18  .531 

71 

426 

3.220 

77  .330 

284 

1  .432 

34  .364 

213 

.806 

19  .337 

72 

432 

3.310 

80  .640 

288 

1  .473 

35  .837 

216 

.828 

20  .165 

73 

438 

3.410 

84  .050 

292 

1  .515 

37  .352 

219 

.852 

21  .017 

74 

444 

3.510 

87  .560 

296 

1  .556 

38  .908 

222 

.877 

21  .894 

75 

450 

3.600 

91  .160 

300 

1  .600 

40  .508 

225 

.899 

22  .793 

76 

456 

3.700 

94  .860 

304 

1.643 

42  .151 

228 

.925 

23  .718 

77 

462 

3.800 

98  .660 

308 

1.708 

43  .859 

231 

.949 

24  .667 

78 

468 

3.900 

102  .560 

312 

1  .735 

45  .594 

234 

.973 

25  .640 

79 

474 

3.990 

106  .550 

316 

1.774 

47  .368 

237 

.998 

26  .638 

80 

480 

4.100 

110  .650 

320 

1  .820 

49  .188 

240 

1.024 

27  .662 

81 

486 

4.200 

114  .850 

324 

1.867 

51  .055 

243 

1.050 

28  .712 

82 

492 

4.310 

119  .160 

328 

1  .912 

52  .967 

246 

1.079 

29  .791 

83 

498 

4.410 

123  .570 

332 

1  .960 

54  .920 

249 

1.103 

30  .894 

84 

504 

4.520 

128  .090 

336 

2.010 

56  .930 

252 

1.130 

32  .024 

85 

510 

4.630 

132  .720 

340 

2.060 

58  .990 

255 

1  .158 

33  .182 

86 

516 

4.740 

137  .460 

344 

2.100 

61  .090 

258 

1  .184 

34  .366 

APPENDIX   A. 


207 


TABLE   LXVIII—  Continued. 


Side  Slopes 


1  ft.  vertical  to  3  ft. 

1  ft.  vertical  to  2  ft. 

1  ft.  vertical  to  1.5  ft. 

hc>ri/<>nt:il 

horizontal 

horizontal 

*J 

§ 

Capacitj 

Total 

Capacity 

Total 

Capacity 

Total 

*s 

H 

Diam- 

for pre- 

ffdiii^ 

capacity 
for  cor- 

Diam 

for  pre- 
ceding 

capacity 
for  cor- 

Diam- 

for pre- 
ceding 

capacity 
for  cor- 

eter 

1  ft.  of 

iv<p<>nd- 

eter 

1ft.  of 

respond- 

eter 

1  ft.  of 

respond- 

depth 

iug  depth 

depth 

ing  depth 

depth 

ing  depth 

Ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

87 

522 

4.850 

142  .310 

348 

2.150 

63  .240 

261 

1.212 

35  .578 

88 

528 

4.960 

147  .270 

352 

2.200 

65  .440 

264 

1.240 

36  .818 

89 

534 

5.070 

152  .340 

356 

2.250 

67.690 

267 

1  .269 

38  .087 

90 

540 

5.190 

157  .530 

360 

2.310 

70.000 

270 

1  .298 

39  .385 

91 

546 

5.300 

162  .830 

364 

2.360 

72  .360 

273 

1.326 

40.711 

92 

552 

5.420 

168  .250 

368 

2.410 

74  .770 

276 

1.355 

42  .066 

93 

558 

5.550 

173  .800 

372 

2.470 

77  .240 

279 

.388 

43.454 

94 

564 

5.670 

179  .470 

376 

2.520 

79  .760 

282 

.417 

44  .871 

95 

570 

5.780 

185  .250 

380 

2.570 

82  .330 

285 

.444 

46  .315 

96 

576 

5.910 

191  .160 

384 

2.620 

84  .950 

288 

.477 

47  .792 

97 

582 

6.020 

197  .180 

388 

2.680 

87  .630 

291 

.504 

49  .296 

98 

588 

6.160 

203  .340 

392 

2.740 

90.370 

294 

1.540 

50.836 

99 

594 

6.290 

209  .630 

396 

2.800 

93  .170 

297 

1.572 

52  .408 

100 

600 

6.420 

216  .050 

400 

2.860 

96  .030 

300 

1  .605 

54  .013 

101 

606 

6.550 

222  .600 

404 

2.910 

98  .940 

303 

1  .633 

55  .646 

102 

612 

6.680 

229  .280 

408 

2.970 

101  .910 

306 

.670 

57  .316 

103 

618 

6.810 

236  .090 

412 

3.030 

104.940 

309 

.701 

59  .017 

104 

624 

6.940 

243  .030 

416 

3.080 

108  .020 

312 

.735 

60  .752 

105 

630 

7.080 

250.110 

420 

3.140 

111  .160 

315 

.769 

62  .521 

100 

636 

7.220 

257  .330 

424 

3.200 

114  .360 

318 

.803 

64  .324 

107 

642 

7  .350 

264  .680 

428 

3.270 

117  .630 

321 

.838 

66  .162 

108 

648 

7.500 

272  .180 

432 

3.330 

120  .960 

324 

.874 

68  .036 

109 

654 

7.630 

279  .810 

436 

3.390 

124.350 

327 

.908 

69  .944 

110 

660 

7.780 

287  .590 

440 

3.450 

127  .800 

330 

1  .942 

71.886 

111 

666 

7.920 

295  .510 

444 

3.520 

131  .320 

333 

1  .979 

73  .865 

112 

672 

8.050 

303  .560 

448 

3  .580 

134  .900 

336 

2.010 

75  .875 

113 

678 

8.200 

311  .760 

452 

3.650 

138  .550 

339 

2.050 

77  .925 

114 

684 

8.350 

320.110 

456 

3.710 

142  .260 

342 

2.090 

80  .015 

115 

690 

8.500 

328  .610 

460 

3.770 

146  .030 

345 

2.120 

82  .135 

116 

696 

8  .650 

337  .260 

464 

3.840 

149  .870 

348 

2.160 

84  .295 

117 

702 

8.800 

346  .060 

468 

3.910 

153  .780 

351 

2.200 

86  .495 

118 

708 

8.950 

355  .010 

472 

3.980 

157  .760 

354 

2.240 

88.735 

119 

714 

9.120 

564  .130 

476 

4.050 

161  .810 

357 

2.280 

91  .015 

120 

720 

9.270 

373  .400 

480 

4.110 

165  .920 

360 

2.310 

93  .325 

121 

726 

9.420 

382  .820 

484 

4.170 

170  .090 

363 

2.350 

95  .675 

122 

732 

9.580 

392  .400 

488 

4.250 

174  .340 

366 

2.390 

98.065 

123 

738 

9.750 

402  .150 

492 

4.330 

178  .670 

369 

2.430 

100  .495 

124 

744 

9.900 

412  .050 

496 

4.390 

183.060 

372 

2.470 

102  .965 

125 

750 

10.050 

422.100 

500 

4.470 

187  .530 

375 

2.510 

105  .475 

126 

756 

10.210 

432  .310 

504 

4.540 

192.070 

378 

2.550 

108  .025 

127 

762 

10  .370 

442  .680 

508 

4.610 

196.680 

381 

2.590 

110.615 

128 

768 

10  .5.50 

453  .230 

512 

4.680 

201  .360 

384 

2.640 

113.255 

129 

774 

10  .710 

463  .940 

516 

4.760 

206  .120 

387 

2.680 

115.935 

130 

780 

10  .870 

474  .810 

520 

4.830 

210  .950 

390 

2.720 

118.655 

208 


PRACTICAL  IRRIGATION. 


TABLE  XLVIII  —  Concluded. 


Side  Slopes 


1  ft.  vertical  to  3  ft. 

1  ft.  vertical  to  2  ft. 

1  ft.  vertical  to  1.5  ft. 

horizontal 

horizontal 

horizontal 

I 

Capacity 

Total 

Capacity 

Total 

Capacity 

Total 

s 
W 

Diam- 
eter 

for  pre- 
ceding 
1  ft.  of 

capacity 
for  cor- 
respond- 

Diam- 
eter 

for  pre- 
ceding 
1  ft.  of 

capacity 
for  cor- 
respond- 

Diam- 
eter 

for  pre- 
ceding 
1  ft.  of 

capacity 
for  cor- 
respond- 

depth 

ing  depth 

depth 

ing  depth 

depth 

ing  depth 

Ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

Ft. 

Acre-ft. 

Acre-ft. 

131 

786 

11  .030 

485  .840 

524 

4.910 

215  .860 

393 

2.760 

121  .415 

132 

792 

11  .200 

497  .040 

528 

4.990 

220  .850 

396 

2.800 

124  .215 

133 

798 

11  .380 

508  .420 

532 

5.060 

225  .910 

399 

2.840 

127  .055 

134 

804 

11  .540 

519  .960 

536 

5.130 

231  .040 

402 

2.880 

129  .935 

135 

810 

11  .720 

531  .680 

540 

5.210 

236  .250 

405 

2.930 

132  .865 

136 

816 

11  .900 

543  .580 

544 

5.290 

241  .540 

408 

2.970 

135  .835 

137 

822 

12  .070 

555  .650 

548 

5.370 

246  .910 

411 

3.020 

138  .855 

138 

828 

12  .250 

567  .900 

552 

5.450 

252  .360 

414 

3.060 

141  .915 

139 

834 

12  .430 

580  .330 

556 

5.530 

257  .890 

417 

3.110 

145  .025 

140 

840 

12.610 

592  .940 

560 

5.610 

263  .500 

420 

3.150 

148  .175 

141 

846 

12  .790 

605  .730 

564 

5.690 

269  .190 

423 

3.190 

151  .365 

142 

852 

12  .980 

618  .710 

568 

5.770 

274  .960 

426 

3.240 

154  .605 

143 

858 

13  .160 

631  .870 

572 

5.850 

280  .810 

429 

3.290 

157  .895 

144 

864 

13  .360 

645  .230 

576 

5.940 

286  .750 

432 

3.330 

161  .225 

145 

870 

13  .540 

658  .770 

580 

6.020 

292  .770 

435 

3.380 

164  .605 

146 

876 

13  .730 

672  .500 

584 

6.100 

298  .870 

438 

3.430 

168  .035 

147 

882 

13  .910 

686  .410 

588 

6.180 

305  .050 

441 

3.470 

171  .505 

148 

888 

14  .100 

700  .510 

592 

6.270 

311  .320 

444 

3.520 

175  .025 

149 

894 

14  .270 

714  .790 

596 

6.350 

317  .670 

447 

3.570 

178  .595 

150 

900 

14  .490 

729  .280 

600 

6.450 

324  .120 

450 

3.620 

182  .215 

151 

906 

14  .670 

743  .950 

604 

6.530 

330  .650 

453 

3.670 

185  .885 

152 

912 

14  .870 

758  .820 

608 

6.620 

337  .270 

456 

3.720 

189  .605 

153 

918 

15  .070 

773  .890 

612 

6.700 

343  .970 

459 

3.770 

193  .375 

154 

924 

15  .270 

789  .160 

616 

6.780 

350  .750 

462 

3.820 

197  .195 

155 

930 

15  .460 

804  .620 

620 

6.880 

357  .630 

465 

3.870 

201  .065 

156 

936 

15  .670 

820  .2CO 

624 

6.970 

364  .600 

468 

3.920 

204  .985 

157 

942 

15  .860 

836  .150 

628 

7.050 

371  .650 

471 

3.970 

208  .955 

158 

948 

16  .080 

852  .230 

632 

7.150 

378  .800 

474 

4.010 

212  .965 

159 

954 

16  .280 

868  .510 

636 

7.240 

386  .040 

477 

4.070 

217  .035 

160 

960 

16  .500 

885  .010 

640 

7.330 

393  .370 

480 

4.120 

221  .155 

APPENDIX  A. 


209 


TABLE  LXIX. 
CIRCULAR    RESERVOIRS. 

Inside  slope  1  to  3.     Outside  slope  1  to  2. 
NOTE.    The  capacity  given  allows  for  no  clearance . 
CASE  1. 


c 

I 
* 

Length    of    side    of 

-r 

M 

Earth  in  embankment 

equivalent   capacity 

"i 

of   square  reservoir 

0 

- 

g, 

& 

a 

If 

<D 

JO 

1 

6 

1 

i 

d 

i 

d 

oS 

I 

1 

ii 

1 

«c 

0 

S 

| 

8 

0 

| 

15 

0 

|S 

5 

s 

? 

_O 

§ 

d 
4 

i 

I 
p 

'as 
d 

l-H 

I 

p 

Ft. 

Ft. 

Acre-ft. 

Gal.  per 
min. 

Cu.  yd. 

Cu.  yd. 

Cu.  yd. 

Ft. 

Ft. 

Ft. 

Ft. 

40 

•2 

52 

.077 

17.3 

102 

116 

130 

68 

35.5 

47.5 

63.5 

3 

58 

.131 

29.7 

217 

242 

267 

78 

53.5 

73.5 

4 

64 

.198 

44.8 

390 

427 

464 

88 

59.5 

83.5 

5 

70 

.279 

63.2 

630 

680 

732 

98 

65.5 

93.5 

6 

76 

.375 

84.8 

946 

1,016 

1,078 

108 

71.5 

103.5 

7 

82 

.488 

110.0 

1,346 

1,429 

1,515 

118 

77.5 

113.5 

8 

88 

.618 

140.0 

1,840 

1,941 

2,050 

128 

83.5 

123.5 

50    2 

62 

.114 

25.7 

121 

137 

154 

78 

44.3 

56.3 

72.3 

3 

68 

.189 

42.8 

254 

282 

310 

88 

62.3 

82.3 

4 

74 

.280 

63.5 

451 

492 

534 

98 

68.3 

92.3 

5 

80 

.387 

87.5 

721 

776 

835 

108 

74.3 

102.3 

6 

86 

.512 

116.0 

1,072 

1,150 

1,218 

118 

80.3 

112.3 

7 

92 

.665 

148.0 

1,510 

1,604 

1,699 

128 

86.3 

122.3 

8 

98 

.817 

185.0 

2,054 

2,165 

2,281 

138 

92.3 

132.3 

60    2 

72 

.157 

35.6 

140 

158 

177 

88 

53.2 

65.2 

81.2 

3 

78 

.259 

58.5 

290 

322 

354 

98 

71.2 

n  .2 

4 

84 

.377 

85.1 

511 

557 

604 

108 

77.2 

101  .2 

5 

90 

.514 

116.0 

811 

873 

937 

118 

83.2 

111  .2 

6 

96 

.670 

151.0 

1,198 

1,283 

1,358 

128 

89.2 

121  .2 

7 

102 

.845 

191.0 

1,679 

1,779 

1,882 

138 

95.2 

131  .2 

8 

108 

1  .044 

236.0 

2,270 

2,387 

2,515 

148 

101  .2 

141.2 

70 

2 

82 

.209 

47.1 

158 

179 

200 

98 

62.1 

74.1 

CO.l 

3 

88 

.339 

76.6 

327 

362 

398 

108 

80.1 

100.1 

4 

94 

.487 

110.0 

572 

622 

674 

118 

86.1 

110.1 

5 

100 

.657 

149.0 

901 

969 

1,039 

128 

92.1 

120. 

6 

106 

.848 

192.0 

1,324 

1,416 

1,498 

138 

98.1 

130. 

7 

112 

1  .062 

240.0 

1,847 

1,954 

2,064 

148 

104.1 

140. 

8 

118 

1.300 

294.0 

2,482 

2,611 

2,747 

158 

110.1 

150. 

80 

2 

92 

.266 

60.3 

177 

200 

224 

108 

71.0 

83.0 

99.0 

3 

98 

.430 

97.0 

363 

402 

441 

118 

89.0 

109.0 

4 

104 

.614 

139.0 

632 

687 

753 

128 

95.0 

119.0 

5 

110 

.819 

185.0 

991 

1,065 

1,140 

138 

101  .0 

129.0 

6 

116 

1.0.50 

237.0 

1,447 

1,549 

1,636 

148 

107.0 

139.0 

7 

122 

1.31 

295.0 

2,013 

2,128 

2,248 

158 

113.0 

149.0 

8 

12S 

1  .586 

359.0 

2,697 

2,833 

2,979 

168 

119.0 

159.0 

210 


PRACTICAL  IRRIGATION. 


TABLE   LXIX— Continued. 


| 

/n 

. 

0> 

Length  of  side  of 

1 

0 

•§ 
1 

a 

as 

Earth  in  embankment 

1" 

equivalent  capacity 
of  square  reservoir 

ameter  bas 

,4 
ft 

0> 

q 

1 
i_ 
o> 

1 

1 

s 

o 

t.  crown 

;.  crown 

;.  crown 

meter  outs 
4-tt.  cro\ 

(0 

9 

3 

1 
1 

hside  base 
ft  crown. 

5 

5 

s 

S 

IH 

S 

3 

'3 

a 

a 
i—  i 

o4 

Ft. 

Ft. 

Ft. 

Acre-ft 

Gal.  per 
min. 

Cu.  yds. 

Cu.  yds 

Cu.  yds 

Ft. 

Ft. 

Ft. 

Ft. 

90 

2 

102 

.333)         75  .3 

196 

221 

247 

118 

79.9 

91  .9 

107  .9 

3 

108 

.531 

120.0 

400 

442 

485 

128 

97.9 

117.9 

4 

114 

.754 

170.0 

693 

747 

813 

138 

103.9 

127.9 

5 

120 

1.000 

226.0 

1,081 

1,161 

1,243 

148 

109.9 

137.9 

6 

126 

1  .270 

287.0 

1,574 

1,681 

1,776 

158 

115.9 

147.9 

7 

132 

1  .570 

355.0 

2,179 

2,305 

2,438 

168 

121.9 

157.9 

8 

138 

1  .901 

430.0 

2,912 

3,060 

3,211 

178 

127.9 

167.9 

100 

2 

112 

.405 

91.6 

214 

242 

270 

128 

88.7 

100.7 

116.7 

3 

118 

.643 

145.0 

437 

483 

529 

138 

106.7 

126.7 

4 

124 

.907 

205.0 

752 

818 

883 

148 

112.7 

136.7 

5 

130 

1.198 

271  .0 

1,172 

1,257 

1,345 

158 

118.7 

146.7 

6 

136 

1  .516 

343.0 

1,700 

1,816 

1,916 

168 

124.7 

156.7 

7 

142 

1  .864 

422.0 

2,347 

2,481 

2,614 

178 

130.7 

166.7 

8 

148 

2.243 

508.0 

3,125 

3,283 

3,447 

188 

136.7 

176.7 

125 

2 

137 

.619 

140.0 

260 

390 

328 

153 

110.8 

122.8 

138.8 

3 

143 

.972 

220.0 

528 

583 

638 

163 

128.8 

148.8 

4 

149 

1.356 

307.0 

904 

984 

1,058 

173 

134.8 

158.8 

5 

155 

1.770 

401.0 

1,397 

1,496 

1,600 

183 

140.8 

168.8 

6 

161 

2.221 

502.0 

2,014 

2,148 

2,364 

193 

146.8 

178.8 

7 

167 

2.708 

613.0 

2,764 

2,916 

3,070 

203 

152.8 

188.8 

8 

173 

3.230 

730.0 

3,662 

3,843 

4,030 

213 

158.8 

198.8 

150 

2 

162 

.878 

198.0 

307 

342 

386 

178 

133.0 

145.0 

161  .0 

3 

168 

1.367 

309.0 

620 

683 

747 

188 

151  .0 

171  .0 

4 

174 

1.891 

428.0 

1,057 

1,144 

1,231 

198 

157.0 

181  .0 

5 

180 

2.459 

556  :0 

1,623 

1,737 

1,855 

208 

163.0 

191  .0 

6 

186 

3.060 

692.0 

2,328 

2,482 

2,613 

218 

169.0 

201.0 

7 

192 

3.710 

838.0 

3,182 

3,356 

3,530 

228 

175.0 

211  .0 

8 

198 

4.390 

993.0 

4,200 

4,400 

4,610 

238 

181  .0 

221  .0 

175 

2 

187 

1  .180 

267.0 

353 

395 

445 

203 

155.2 

167.2 

183.2 

3 

193 

1.830 

414.0 

712 

784 

855 

213 

173.2 

193.2 

4 

199 

2.523 

571  .0 

1,208 

1,306 

1,405 

223 

179.2 

203.2 

5 

205 

3.260 

737.0 

1.848 

1,977 

2,110 

233 

185  .2 

213.2 

6 

211 

4.035 

913.0 

2,641 

2,815 

2,962 

243 

191  .2 

223.2 

7 

217 

4.860 

1,099.0 

3,700 

3,795 

3,990 

253 

197.2 

233  .2 

8 

223 

5.740 

1,297.0 

4,732 

4,960 

5,190 

243 

203.2 

243.2 

200 

2 

212 

1.528 

346.0 

400 

451 

503 

228 

177.3 

189.3 

205.3 

3 

218 

2.360 

535.0 

803 

884 

965 

238 

195.3 

215.3 

4 

224 

3.240 

732.0 

1,358 

1,469 

1,581 

248 

201  .3 

225.3 

5 

230 

4.170 

943.0 

2,074 

2,216 

2,364 

258 

207.3 

235.3 

6 

236 

5.150 

1,163  .0 

2,957 

3,150 

3,314 

268 

213.3 

245.3 

7 

242 

6.180 

1,397.0 

4,017 

4,230 

4,450 

278 

219.3 

255.3 

8 

248 

7.26 

1,640  .0 

5,272 

5,520 

5,780 

288 

225.3 

265.3 

250 

2 

262 

2.360 

534.0 

493 

556 

620 

278 

221.8 

233.8 

249.8 

3 

268 

3.630 

820.0 

987 

1,084 

1,184 

288 

239.8 

259.8 

4 

274 

4.950 

1,218.0 

1,660 

1,794 

1,930 

298 

245.8 

269.8 

5 

280 

6.250 

1,413.0 

2,527 

2,696 

2,873 

318 

' 

251  .8 

279  .8 

6 

286 

7.700 

1,739  .0 

3,586 

3,815 

4,012 

328 

267  .8  ' 

289.8 

7 

292 

9.280 

2,098  .0 

4,850 

5,110 

5,365 

338 

273  .8  1 

299.8 

8 

298 

10  .840 

2,453  .0 

6,340 

6,640 

6,940 

348 

279  .8  : 

509.8 

APPENDIX    A. 


211 


TABLE   LXIX— Continued. 


•8 

I 

Length   of   side   of 

1 

* 

Earth  in  embankment 

I 

equivalent  i-:t|..-i.-ity 
of  square  reservoir 

5 

1 

1 

~ 

d 

If 

I  = 

1 

1 

| 

o 

I 

I 

I 

g 

J4 

I 

I  2 

1 

1 

u 

V 

e 

v 

£"* 

OJ 

tJ 

-3 

•~  ^ 

s 

1 

3 

i 

S 

41 

3 

5 

1 

1 

I5 

Ft. 

Ft. 

Ft. 

Acre-ft. 

Gal.  per 
min. 

Cu.  yds. 

Cu.  yds. 

Cu.  yds 

Ft. 

Ft. 

Ft. 

Ft. 

300 

2 

312 

3.370 

762.0 

586 

661 

737 

328 

266.0 

278  .01294  .0 

3 

318 

5.170 

1,167  .0 

1,170 

1,285 

1,401 

338 

284.0301  .0 

4 

324 

7.010 

1,586.0 

1,963 

2,111 

2,281 

348 

290.0314.0 

5 

330 

8.940 

2,020  .0 

2,978 

3,176 

3,383 

358 

296  .0  32  1  .0 

6 

«6  10  .940 

2,476  .0 

4,215 

4,480 

4,710 

368 

302  .0  334  .0 

7 

342  13  .000 

2,941  .0 

5,690 

5,980 

6,282 

378 

308.0344.0 

8 

348  15  .150 

3,428  .0 

7,420 

7,750 

8,110 

388 

314  .0  354  .0 

350 

2 

362 

4.570 

1,034  .0 

680 

765 

853 

378 

310.4 

322  .4  338  .0 

3 

368 

6.970 

1,574.0 

1,353 

1,486 

1,620 

388 

32S  A 

348.4 

4 

374 

9.450 

2,137  .0 

2,268 

2,448 

2,629 

398 

334  .4(358  .4 

5 

380 

12  .010 

2,717  .0 

3,329 

3,657 

3,892 

418 

340  .4 

368.4 

6 

386  14  .650 

3,311  .0 

4,845 

5,150 

5,410 

428 

346.4 

378  .4 

7 

392  17  .380 

3,930  .0 

"6,520 

6,860 

7,200 

438 

352.4 

388.4 

8 

398  20  .200 

4,563  .0 

8,490 

8,870 

9,270 

448 

358.4 

398.4 

400 

2 

412 

5.940 

1,342.0 

773 

870 

970 

428 

354.6 

366.6 

382.4 

3 

418 

9.040 

2,024  .0 

1,538 

1,687 

1,837 

438 

372  .6 

392.6 

4 

424 

12  .230 

2,766  .0 

2,568 

2,772 

2,977 

448 

378  .6  402  .6 

5 

430 

15  .510 

3,507  .0 

3,879 

4,136 

4,400 

458 

-5X1  6412.6 

6 

436 

18.900 

4,270  .0 

5,471 

5,810 

6,110 

468 

WO  .6  422  .6 

7 

442-22  .370 

5,055  .0 

7,360    7,730    8,120 

478 

396  .6  432  .6 

8 

448  2.5  .930 

5,862  .0 

9,560    9,990  10,440 

488 

102  6442.6 

450 

2 

462 

7.490 

1,692.0 

865 

1)75     1,085 

478 

399.0 

411  .0427.6 

3 

468 

11.380 

2,576  .0 

1,720 

1,888    2,057 

488 

117  .0437.0 

4 

474 

15  .390 

3,479  .0 

2,872 

3,098 

3,328 

498 

123  .0417  .0 

5 

480 

19  .470 

4,402  .0 

4,337 

4,615 

4,910 

508 

120  .0  4.57  .0 

6 

486 

23.670 

5,353  .0 

6,102 

6,480 

6,810 

518 

435  .0  467  .0 

7 

402 

28.000 

6,332  .0 

8,195 

8,610 

9,030 

528 

441  .0477.0 

8 

4<)8 

32.380 

7,324  .0 

10,640 

11,100 

11,600 

538 

117  .0  187  .0 

500 

2 

512 

9.250 

2,084  .0 

960 

1,079 

1,201 

528 

443.0 

1.55.0471  .0 

3 

518  14  .000 

3,165  .0 

1,904 

2,088 

2,273 

538 

161  .0481  .0 

4 

524  18  .900 

4,267  .0 

3,175 

3,424 

3,677 

548 

467  .0  491  .0 

5 

530 

23.900 

5,404  .0 

4,786 

5,100 

5,420 

558 

473  .0  501  .0 

6 

536 

29.000 

6,556  .0 

6.735 

7,140 

7,500 

568 

17'.)  .0511.0 

7 

542 

34.270 

6,751  .0 

9,030 

9,490 

9,950 

578 

485.0521  .0 

8 

.548 

39.600 

8,952  .0 

11,710 

12,220 

12,760 

588 

491  .0  531  .0 

550 

2 

562 

11  .140 

2,520  .0 

1,050 

1,184 

1,318 

578 

487.6 

1'.)'.)  6516.6 

3 

568 

16.890 

3,821  .0 

2,087 

2,288 

2,491 

588 

505  .0  525  .6 

4 

574 

22  .770 

5,150  .0 

3,478 

3,750 

4,026 

598 

511.6535.6 

5 

580 

28  .780 

6,508  .0 

5,234 

5,580 

5,930 

608 

517  .6  545  .6 

6 

586 

34.900 

7,900  .0 

7.360 

7,820 

8,200 

618 

523  6  555  .6 

7 

59041.100 

9,300  .0 

9,870 

10,380 

10,860 

628 

529  .6  565  .6 

8 

596  47  .500 

10,728  .0 

12,780 

13,330 

13,920 

638 

535  .6  575  .6 

600 

2 

112  13  .230 

2,992  .0 

1,113 

1,289 

1,435 

628 

531.8 

543  .8  559  .8 

3 

ilx_>o.040 

4,534  .0 

2,270 

2,489 

2,712 

638 

549  .8  569  .8 

4    62427.000 

6,102  .0 

3,780 

4,080 

4,377 

648 

5.5.5  >  :,79  .8 

5    63034.100 

7,700  .0 

5,687 

6,050 

6,435 

658 

561  .x.589.8 

6    636  41  .300 

9,348  .0 

7,993 

8,480 

8,900 

668 

567  .8  599  .8 

7   64248.700 

10,994  .0 

10,697 

11,240  11.7x0 

678 

573  .8  609  .8 

8    64856.100 

12,778  .0  13,850 

14,4.50  15,110      6S8 

579  .8  619  .8 

212 


PRACTICAL  IRRIGATION. 


TABLE  LXX. 
CIRCULAR    RESERVOIRS. 

Inside  slope  1  to  2.     Outside  slope  1  to 

NOTE.     The  capacity  given  allows  for  no  clearance. 

CASE  2. 


0 

. 

I 

Length  of  side  of  equiv- 

°2 

•a 

•«•; 

J3 

Earth  in  embankment 

'j| 

alent   capacity  of 

§ 

?! 

§S 

square  reservoir 

1 

(H 
® 

"S 

I 

neter  top 

! 

I 

2 

crown 

O 
b 

ii 

&  <•> 

1 

"S 

f 

<D 

13 

ide  base 
crown 

3 

• 

o 

.j 

4> 

£ 

l 

1 

•2<£ 

s 

5 

E 

3 

3 

s 

5 

H 

tH 

0« 

Ft. 

Ft. 

Ft. 

Acre-ft. 

Gal.  per 
min. 

Cu.  yd. 

Cu.  yd. 

Cu.  yd. 

Ft. 

Ft. 

Ft. 

Ft. 

40 

2 

48 

.070 

15.8 

76 

89 

103 

62 

35.5 

43.5 

57.5 

3 

52 

.115 

26.0 

153 

175 

198 

69 

47.5 

64.5 

4 

56 

.168 

37.9 

263 

295 

328 

76 

51.5 

71.5 

5 

60 

.229 

51  .6 

410 

452 

496 

83 

55.5 

78.5 

6 

64 

.298 

67.3 

586 

650 

706 

90 

59.5 

85.5 

7 

68 

.376 

85.0 

827 

897 

965 

97 

63.5 

92.5 

8 

72 

.465 

105.0 

1,106 

1,188 

1,275 

104 

67.5 

99.5 

50 

2 

58 

.106 

23.8 

91 

107 

123 

72 

44  .3 

52.3 

66.3 

3 

62 

.170 

38.5 

182 

207 

234 

79 

56.3 

73.3 

4 

66 

.244 

55.1 

310 

346 

384 

86 

60.3 

80.3 

5 

70 

.327 

74.0 

479 

526 

576 

93 

64.3 

87.3 

6 

74 

.421 

95.2 

691 

751 

815 

100 

68.3 

94.3 

7 

78 

.526 

119.0 

951 

1,029 

1,107 

107 

72.3 

101.3 

8 

82 

.641 

145.0 

1,264 

1,356 

1,453 

114 

76.3 

108.3 

60 

2 

68 

.148 

33.4 

106 

124 

143 

82 

53.2 

61.2 

75.2 

3 

72 

.237 

53.4 

211 

240 

270 

89 

65.2 

82.2 

4 

76 

.335 

75.8 

356 

397 

440 

96 

69.2 

89.2 

5 

80 

.445 

100.3 

547 

600 

656 

103 

73.2 

96.2 

6 

84 

.566 

128.0 

785 

853 

923 

110 

77.2 

103.2 

7 

88 

.700 

158.0 

1,075 

1,162 

1,248 

117 

81.2 

110.2 

8 

92 

.846 

191  .0 

1,423 

1,524 

1,630 

124 

85.2 

117.2 

70 

2 

78 

.198 

44.7 

121 

141 

163 

92 

62.1 

70.1 

84.1 

3 

82 

.313 

70.7 

240 

272 

306 

99 

74.1 

91.1 

4 

86 

.440 

99.5 

.403 

449 

496 

106 

78.1 

98.1 

5 

90 

.580 

131  .0 

616 

475 

736 

113 

82.1 

105.1 

6 

94 

.733 

163.0 

879 

954 

1,032 

120 

86.1 

112.1 

7 

98 

.899 

203.0 

1,200 

1,294 

1,388 

127 

90.1 

119.1 

8 

102 

1.080 

244.0 

1,582 

1,690 

1,807 

134 

94.1 

126.1 

80 

2 

88 

.255 

57.5 

136 

159 

182 

102 

71  .0 

79.0 

93.0 

3 

92 

.400 

91  .0 

268 

304 

341 

109 

83.0 

100.0 

4 

96 

.560 

126.0 

450 

500 

552 

116 

87.0 

107.0 

5 

100 

.734 

166.0 

685 

749 

816 

123 

91  .0 

114.0 

6 

104 

.921 

208.0 

973 

1,055 

1,139 

130 

95.0 

121.0 

7 

108 

1  .124 

254.0 

1,325 

1,427 

1,527 

137 

99.0 

128.0 

8 

112 

1.341 

313.0 

1,741 

8,158 

1,984 

144 

103.0 

135.0 

APPENDIX    .1. 


213 


TABLE  LXX— Continued. 


0 

. 

« 

Length  of  side  of  equiv- 

3 

73 

Js 

Earth  in  embankment 

3 

a  If  nt  capacity  of 

a 

'x 

C 

s 

square  reservoir 

i 

1 

i 

1 

d 

d 

1 

a 

ij 

i 

§• 

2  a 

i 

& 

i 

2 

! 

91 

a 

1 

£ 

0 

i 

JB 

1 

tl 

•§  0 

i 

5 

S 

I 

i 

i 

i 

5 

I 

a 

M 

|fi 

Ft. 

Ft. 

Ft. 

Acre-ft. 

Gal.  per 

min. 

Cu.  yd. 

Cu.  yd. 

Cu.  yd. 

Ft. 

Ft. 

Ft. 

Ft. 

90 

2 

98 

.319 

72.0 

151 

176 

202 

112 

V9.9 

87.9 

101.9 

3 

102 

.500 

113.0 

297 

336 

377 

119 

91.9 

108.9 

4 

106 

.695 

157.0 

496 

551 

608 

126 

95.9 

115.9 

5 

110 

.906 

204.0 

752 

824 

896 

133 

99.9 

122.9 

6 

114 

1  .131 

255.0 

1,068 

1,156 

1,249 

140 

103.9 

129.9 

7 

118 

1.373 

310.0 

1,530 

1,559 

1,790 

147 

107.9 

136.9 

8 

122 

1.632 

369.0 

1,898 

2,026 

2,161 

154 

111.9 

143.9 

100 

2 

108 

.391 

88.3 

166 

194 

222 

122 

88.7 

96.7 

110.7 

3 

112 

.608 

137.0 

326 

369 

413 

129 

100.7 

117.7 

4 

116 

.843 

190.0 

533 

602 

664 

136 

104.7 

124.7 

5 

120 

1.094 

147.0 

821 

898 

976 

143 

108.7 

131  .7 

6 

124 

1  .362 

308.0 

1,162 

1,258 

1,355 

150 

112.7 

138.7 

7 

128 

1  .648 

372.0 

1,572 

691 

1,809 

157 

116.7 

145.7 

8 

132 

1  .955 

441.0 

2,055 

2,193 

2,337 

164 

120.7 

152.7 

125 

2 

133 

.601 

136.0 

204 

237 

272 

147 

110.8 

118.8 

132.8 

3 

137 

.930 

210.0 

398 

449 

503 

154 

122.8 

139.8 

4 

141 

1.278 

288.0 

659 

730 

803 

161 

126.8 

146.8 

5 

145 

1  .647 

372.0 

992 

1,082 

1,176 

168 

130.8 

153.8 

6 

149 

2.035 

460.0 

1,397 

1,513 

1,626 

175 

134.8 

160.8 

7 

153 

2.448 

553.0 

1,883 

2,023 

2,161 

182 

138.8 

167.8 

8 

157 

2.880 

650.0 

2,452 

2,613 

2,779 

189 

142.8 

174.8 

150 

2 

158 

.855 

193.0 

242 

281 

321 

172 

133.0 

141.0 

155.0 

3 

162 

1  .316 

297.0 

470 

530 

592 

179 

145.0 

162.0 

4 

166 

1  .800 

412.0 

776 

858 

943 

186 

149.0 

169.0 

5 

170 

2.310 

522.0 

1,163 

1,278 

1,370 

193 

153.0 

176.0 

6 

174 

2.845 

643.0 

1,634 

1,766 

1,897 

200 

157.0 

183.0 

7 

178 

3.400 

769.0 

2,194 

2,355 

2,513 

207 

161.0 

190.0 

8 

182 

3.990 

901.0 

2,848 

3,032 

3,223 

214 

165.0 

197.0 

175 

2 

183 

1  .157 

261.0 

280 

325 

371 

197 

155.2 

163.2 

177.2 

3 

187 

1.774 

400.0 

542 

611 

682 

204 

167.2 

184.2 

4 

191 

2.417 

546.0 

893 

987 

1,083 

211 

171.2 

191  .2 

5 

195 

3.090 

698.0 

1,334 

1,453 

1,576 

218 

175.2 

198.2 

6 

199 

3.790 

856.0 

1,869 

2,019 

2,167 

225 

179.2 

205.2 

7 

203 

4.510 

1,019.0 

2,506 

2,686 

2,863 

232 

183.2 

212.2 

8 

207 

5.270 

1,190.0 

3,245 

3,450 

3,670 

239 

187.2 

219.2 

200 

2 

20S 

1.500 

339.0 

317 

369 

420 

222 

177.3 

185.3 

199.3 

3 

212 

2.297 

519.0 

614 

692 

771 

229 

189.3 

206.3 

4 

216 

3.120 

705.0 

1,009 

1,114 

1,220 

236 

193.3 

213.3 

5 

220 

3.980 

900.0 

1,505 

1,639 

1,776 

243 

197.3 

220.3 

6 

224 

4.860 

1,098.0 

2,105 

2,274 

2,436 

250 

201  .3 

227.3 

7 

228 

5.800 

1,306.0 

2,814 

3,020 

3,215 

257 

205.3 

234.3 

8 

232 

6.750 

1,523.0 

3,640 

3,870 

4,110 

264 

209.3 

241.3 

250 

2 

258 

2.310 

521.0 

393 

456 

519 

272 

221.8 

229.8 

243.8 

3 

262 

3.550 

802.0 

758 

854 

950 

279 

233.8 

250.8 

4 

266 

4.810 

1,085.0 

1,241 

1,371 

1,500 

286 

237.8 

257.8 

5 

270 

6.100 

1,375.0 

1,847 

2,011 

2,176 

293 

241.8 

264.8 

6 

274 

7  .430 

1,675.0 

2,575 

2,779 

2,980 

300 

245.8 

271.8 

7 

278 

8.820 

1,988.0 

3,440 

3,680 

3,920 

307 

249.8 

278.8 

8 

282 

10  .220 

2,305  .0 

4,430 

4,710 

4,990 

314 

253.8 

285.8 

214 


PRACTICAL  IRRIGATION. 


TABLE   LXX  —  Concluded . 


V 

® 

0) 

•d 

Length  of  side  of  equiv- 

*3 

«§ 

j^ 

Earth  in  embankment 

1 

alent  capacity  of 

.s 

© 

1 

>-i 

S 

!s 

square  reservoir 

I 

,g 
"a 

J 

1 

'Z 

_ 

i§ 

$ 

a 

is 

h 

C 

"S 

a 
P 

1 

9 

g 

1 

S 
3 

i 

0 

o 
£ 
u 

h 

O 

(-1  4» 

<P<M 

i4 

o> 
•o 

o 

e 
g 

! 

g 

3 

^ 

o 

^J 

jj 

a 

°3 

a 

'•2  d 

S 

S 

£ 

3 

3 

S 

.5 
S 

a 

M 

M 

§3 

Ft. 

Ft. 

Ft. 

Acre-ft. 

Gal.  per 
min. 

Cu.  yd. 

Cu.  yd. 

Cu.  yd. 

Ft. 

Ft. 

Ft. 

Ft. 

300 

2 

308 

3.330 

752.0 

469 

544 

618 

322 

266.0 

274.0 

288.0 

3 

312 

5.060 

1,142.0 

903 

1,016 

1,129 

329 

278.0 

295.0 

4 

316 

6.850 

1,543.0 

1,474 

1,627 

1,780 

336 

282.0 

302.0 

5 

320 

8.670 

1,955.0 

2,190 

2,383 

2,576 

343 

286.0 

309.0 

6 

324 

10  .540 

2,380  .0 

3,049 

3,290 

3,520 

350 

290.0 

316.0 

7 

328 

12  .450 

2,812  .0 

4,060 

4,350 

4,620 

357 

294.0 

323.0 

8 

332 

14  .410 

3,257  .0 

5,220 

5,540 

5,880 

364 

298.0 

330.0 

350 

2 

358 

4.520 

1,021  .0 

544 

631 

717 

372 

310.4 

318.4 

332.4 

3 

362 

6.860 

1,550.0 

1,046 

1,176 

1,308 

379 

322  .4 

339.4 

4 

366 

9.250 

2,086  .0 

1.707 

1,882 

2,057 

386 

326.4 

346.4 

5 

370 

11  .700 

2,641  .0 

2,530 

2,751 

2,976 

393 

330.4 

353.4 

6 

374 

14.06 

3,178  .0 

3,520 

3,790 

4,060 

400 

334.4 

360.4 

7 

378 

16  .730 

3,781  .0 

4,680 

5,010 

5,320 

407 

338.4 

367.4 

8 

382 

19  .340 

4,368  .0 

6,020 

6,390 

6,770 

414 

342.4 

374.4 

400 

2 

408 

5.890 

1,330  .0 

620 

718 

816 

422 

354.6 

362.6 

376.6 

3 

412 

8.920 

2,014  .0 

1,190 

1,336 

1,487 

429 

366.6 

383.6 

4 

416 

12  .000 

2,712  .0 

1,940 

2,140 

2,338 

436 

370.6 

390.6 

5 

420 

15  .160 

3,424  .0 

2,876 

3,120 

3,376 

443 

374.6 

397.6 

6 

424 

18.37 

4,150  .0 

3,990 

4,300 

4,600 

450 

378.6 

404.6 

7 

428 

21  .620 

4,888  .0 

5,300 

5,670 

6,020 

457 

382.6 

411  .6 

8 

432 

24  .970 

5,648  .0 

6,810 

7,220 

7,650 

464 

386.6 

418.6 

450 

2 

458 

7.430 

1,678.0 

696 

805 

915 

472 

399.0 

407.0 

421  .0 

3 

462 

11  .230 

2,537  .0 

1,333 

1,500 

1,666 

479 

411.0 

428.0 

4 

466 

15  .120 

3,420  .0 

2,170 

2,395 

2,612 

486 

415.0 

435.0 

5 

470 

19  .080 

4,310  .0 

2,220 

3,490 

3,776 

493 

419.0 

442.0 

6 

474 

23  .080 

5,216  .0 

4,470 

4,800 

5,140 

500 

423.0 

449.0 

7 

478 

27  .200 

6,148  .0 

5,930 

6,330 

6,730 

507 

427.0 

456.0 

8 

482 

31  .300 

7,083  .0 

7,600 

8,060 

8,550 

514 

431.0 

463.0 

500 

2 

508 

9170 

2,067  .0 

772 

893 

1,014 

522 

443.0 

451.0 

465.0 

3 

512 

13  .840 

3,130  .0 

1,478 

1,661 

1,845 

529 

455.0 

472.0 

4 

516 

18  .600 

4  203  .0 

2,405 

2,652 

2,895 

536 

459.0 

479.0 

5 

520 

23  .430 

5,300  .0 

3,560 

3,870 

4,176 

543 

463.0 

486.0 

6 

524 

28  .360 

6,408  .0 

4,930 

5,310 

5,680 

550 

467.0 

493.0 

7 

528 

33  .400 

7,537  .0 

6,550 

6,990 

7,430 

557 

471  .0 

500.0 

8 

532 

38  .400 

8,685  .0 

8,390 

8,900 

9,430 

564 

475.0 

507.0 

550 

2 

558 

11  .080 

2,500  .0 

847 

981 

1,113 

572 

487.6 

495.6 

509.6 

3 

562 

16  .730 

3,780  .0 

1,622 

1,822 

2,024 

579 

499.6 

516.6 

4 

566 

22  .450 

5,075  .0 

2,637 

2,908 

3,174 

586 

503.6 

523.6 

5 

570 

28  .300 

6,390  .0 

3,900 

4,240 

4,576 

593 

507.6 

530.6 

6 

574 

34  .200 

7,726  .0 

5,400 

5,820 

6,230 

600 

511  .6 

537.6 

7 

578 

40  .200 

9,084  .0 

7,170 

7,660 

8,140 

607 

515.6 

544.6 

8 

582 

46  .200 

10,428  .0 

9,380 

9,740 

10,320 

614 

519.6 

551  .6 

600 

2 

608 

13  .150 

2,972  .0 

923 

1,067 

1,212 

622 

531.8 

539  .8 

553.8 

3 

612 

19  .850 

4,493  .0 

1,766 

1,983 

2;203 

629 

543.8 

560.8 

4 

616 

26  .640 

6,020  .0 

2,871 

3,160 

3,450 

636 

547.8 

567.8 

5 

620 

33  .700 

7,582  .0 

4,240 

4,610 

4,976 

643 

551  .8 

574.8 

6 

624 

40  .500 

9,154.0 

5,880 

6,330 

6,770 

650 

555.8 

581.8 

7 

628 

47  .600 

10,730  .0 

7,790 

8,320 

8,840 

657 

559.8 

588.8 

8 

632 

54  .800 

12,358  .0 

9.980 

10,570 

11,200 

664 

563.8 

595.8 

APPENDIX    A. 


215 


TABLE   LXXI. 
RESERVOIR    CAPACITY. 

CASE  I. 
NOTE.     The  capacity  given  allows  for  no  clearance. 


Diam- 
eter, 

Depth, 

Capacity, 

Diam- 
eter, 

Depth, 

Capacity, 

•  Diam- 
eter, 

Depth, 

Capacity, 

Ft. 

Ft. 

Acre-ft. 

Ft. 

Ft. 

Acre-ft. 

Ft. 

Ft. 

Acre-ft. 

800 

2 

23.4 

6 

686.0 

10 

6,550.0 

3 

35.4 

7 

802.0 

11 

7,210  .0 

4 

47.5 

8 

920.0 

12 

7,870  .0 

5 

59.9 

9 

1,035.0 

7,000 

2 

1,768  .0 

6 

72.3 

10 

1,153.0 

3 

2,660  .0 

7 

85.1 

11 

1,270.0 

4 

3,544  .0 

8 

98.0 

12 

1,392  .0 

5 

4,434  .0 

9 

110.9 

3,000 

2 

325.3 

6 

5,315  .0 

10 

124.3 

3 

490.0 

7 

6,212  .0 

11 

137.9 

4 

654.0 

8 

7,111  .0 

12 

151.1 

5 

820.0 

9 

8,010  .0 

1,000 

2 

36.5 

6 

985.0 

10 

8,910  .0 

3 

55.0 

7 

1,150.0 

11 

9,810  .0 

4 

73.9 

8 

1,320.0 

12 

10,700  .0 

5 

92.8 

9 

1,484  .0 

8,000 

2 

2,316  .0 

6 

112.0 

10 

1,653.0 

3 

3,470  .0 

7 

131.5 

11 

1,820.0 

4 

4,623  .0 

8 

151.1 

12 

1,991  .0 

5 

5,792  .0 

9 

171.0 

4,000 

2 

578.0 

6 

6,950  .0 

10 

191.1 

3 

870.0 

7 

8,122  .0 

. 

11 

212.0 

4 

1,160.0 

8 

9,290.0 

12 

232.0 

5 

1,453  .0 

9 

10,440  .0 

1,500 

2 

81.8 

6 

1,745.0 

10 

11,610.0 

3 

123.0 

7 

2,040  .0 

11 

12,820  .0 

4 

164.8 

8 

2,336  .0 

12 

13,970  .0 

5 

207  .0 

9 

2,628  .0 

9,000 

2 

2,920  .0 

6 

249.2 

10 

2,926  .0 

3 

4,390  .0 

7 

292.0 

11 

3,222  .0 

4 

5,855  .0 

8 

335.0 

12 

3,520  .0 

5 

7,320  .0 

9 

378.0 

5,000 

2 

903.0 

6 

8,796  .0 

10 

417.0 

3 

1,357  .0 

7 

10,275  .0 

11 

465.0 

4 

1,812.0 

8 

11,720.0 

12 

508.0 

5 

2,266.0 

9 

13,210  .0 

2,000 

2 

145.0 

6 

2,720  .0 

10 

14,680  .0 

3 

218.3 

7 

3,177  .0 

11 

16,160.0 

4 

292.0 

8 

3,640  .0 

12 

17,640  .0 

5 

366.0 

9 

4,100  .0 

10,000 

2 

3,603  .0 

6 

440.0 

10 

4,550  .0 

3 

5,415  .0 

7 

515.0 

11 

5,025  .0 

4 

7,230  .0 

8 

590.5 

12 

5,475  .0 

5 

9,050  .0 

9 

666.0 

6,000 

2 

1,300.0 

6 

10,860  .0 

10 

742.0 

3 

1,951  .0 

7 

12,660  .0 

11 

820.0 

4 

2,607  .0 

8 

14,490  .0 

12 

896.0 

5 

3,260.0 

9 

16,290  .0 

2,500 

2 

226.5 

6 

3,920  .0 

10 

18,120  .0 

3 

340.6 

7 

4,580  .0 

11 

19,960  .0 

4 

455  .0 

8 

5,230  .0 

12 

21,740.0 

5 

570.0 

9 

5.900.0 

216 


PRACTICAL  IRRIGATION. 


TABLE   LXXII. 

TABLE    OF    COEFFICIENTS    TO    ASSIST    IN    CALCULATIONS    TO 

DETERMINE    THE    CUBIC    YARDS    OF    EARTH    IN 

RESERVOIR    EMBANKMENTS    WITH    4-FOOT 

CROWN    AND    OF    VARIOUS    DEPTHS. 

Cubic  yards  =  a  +  bd .     d  =  inside  base  diameter. 


Depth 

Case  1 
a 

Case  1 
b. 

Case  2 
a 

Case  2 
b 

Case  3 
a 

CaseS 
ft 

Ft. 
2 

32 

2.10 

19 

1.75 

16 

1  .57 

3 

81 

4.02 

46 

3.23 

39 

2.97 

4 

166 

6.52 

90 

5.12 

75 

4.66 

5 

296 

9.60 

155 

7.43 

127 

6.70 

6 

483 

13.30 

246 

10.13 

200 

9.09 

7 

728 

17.50 

367 

13.24 

295 

11.82 

8 

1,047 

22.40 

518 

16.80 

429 

14.90 

9 

1,450 

27.80 

769 

20.70 

570 

18.35 

10 

1,942 

33.80 

1,022 

25.10 

752 

22.10 

11 

2,544 

40.40 

1,325 

29.80 

972 

26.25 

12 

3,341 

47.50 

1,683 

35.00 

1,230 

30.75 

13 

3,963 

55.30 

2,095 

40.50 

1,529 

35.60 

14 

5,023 

63.60 

2,579 

46.50 

1,875 

40.75 

15 

6,113 

72.50 

3,127 

52.90 

2,270 

46.30 

16 

2,710 

52  .15 

17 



j 

3,  '21  5 

58  '40 

18 

3  770 

65  .00 

19 

4,385 

71  ^90 

20 

5  070 

79  .20 

22 

24 

I 

8  500 

111  75 

26 

10^670 

130  10 

28 

13  200 

150  .00 

30 





16^080 

171  .00 

APPENDIX   A. 


217 


TABLE   LXXIII. 

DIMENSIONS    OF    CIRCULAR    RESERVOIRS    OF    MOST 
ECONOMIC    SECTION    WITH    4-FOOT    CROWN. 


CASE  1.     Clearance  = 


+1Q  d 


feet. 


Inside  base 
diameter 

Depth 

of  embank- 
ment 

Depth  of 

water 

Capacity 

Volume  earth 
n  embankment 

Volume  earth 
per  acre-ft. 

Ft. 

Ft. 

Ft. 

Aore-ft. 

Cu.  yd. 

Cu.  yd. 

50 

1  .68 

.66 

.033 

103 

3,120 

100 

1  .99 

.79 

.149 

239 

1,605 

200 

2  .42                .97 

.718 

612 

853 

300 

2  .74              1  .10 

1.820 

1,103 

607 

400 

3  .02              1  .22 

3.540 

1,705 

482 

600 

3.47 

1  .40 

9.210 

3,182 

345 

800 

3.85 

1.55 

18.100 

5,042 

279 

1,000             4.19 

1.69 

30  .700 

7,260 

236 

1,200 

4  .49 

1.81 

47  .400 

9,776 

206 

1,400 

4.77 

1.92 

68.500 

12,642 

185 

1,600 

5.03 

2.03 

95.200 

15,810 

166 

Clearance  =  3  feet. 


1,600 

4.225 

1  .225 

56.8 

11,650 

205.0 

2,000 

4.225 

.225 

88.5 

14,520 

164.0 

3000 

4.225 

.225 

199.0 

21,680 

109.0 

4,000 

4.225 

.225 

354.0 

29,800 

84.3 

6,000 

4.225 

.225 

795.0 

43,200 

54.4 

8,000 

4.225 

.225 

1,413  .0 

57,400 

40.6 

10,000 

4.225 

.225 

2,206.0 

71,800 

32.5 

218 


PRACTICAL  IRRIGATION. 


TABLE   LXXIV. 

DIMENSIONS    OF    CIRCULAR    RESERVOIRS    OF    MOST    ECONOMIC 
SECTION   WITH   FOUR-FOOT  CROWN. 


CASE  2.     Clearance  =  .( 


Inside  base 
diameter 

Depth 

of  embank- 
ment 

Deptb  of 
water 

Capacity 

Volume  earth 
in  embankment 

Volume  earth 
per  acre-ft. 

Ft. 

Ft. 

Ft. 

Acre-ft. 

Cu.  yd. 

Cu.  yd. 

50 

1.74 

.72 

.034 

86.4 

2,540 

100 

2.05 

.85 

.153 

200.0 

1,265 

200 

2.48 

.03 

.755 

510.0 

675 

300 

2.81 

.17 

1  .920 

912.0 

475 

400 

3.08 

.28 

3.730 

1,394  .0 

374 

600 

3.53 

.46 

9.560 

2,577  .0 

270 

800 

3.93 

.63 

18  .950 

4,071  .0 

215 

1,000 

4  .26 

.76 

32  .000 

5,785  .0 

181 

1,200 

4.57 

.89 

49  .300 

7,784  .0 

158 

1,400 

4.85 

2  00 

71  .300 

10,024  .0 

141 

1,600 

5.11 

2.11 

97  .900 

12,494  .0 

128 

Clearance  =  3  feet. 


1,600 

4.30 

1  .30 

60.2 

9,380 

155.7 

2,000 

4  .30 

1  .30 

94.0 

11,690 

124.4 

3,000 

4.30 

1  .30 

212.0 

17,450 

82.3 

4,000 

4  .30 

1  .30 

376.0 

23,200 

61  .7 

6,000 

4  .30 

1  .30 

845.0 

34,750 

41.1 

8,000 

4.30 

1  .30 

1,501  .0 

46,300 

30.9 

10,000 

4.30 

1.30 

2,345  .0 

57,800 

24.6 

APPENDIX   B. 
CIRCULAR    EMBANKMENTS. 

VOLUME  of  embankment  =  2  *  (r  +  HS  +     ^)  H  (W  +  HS) 


=  approximately,  2-r+HS+         w  +  H 

When  P  =  S  =  T,  Volume  =  2-(r  +HT  +^\  (W+HT)H. 

\  ^i  / 

Volume  of  water  =  ^  (rt3-r3)  =  (approximately)  TT  (r+  -  -  )   /i 

O  A3  \  2    ' 

cu.  ft. 
Where  h  =  depth  of  water  =  H  —  b. 

Formulae  may  be  deduced  for  the  economic  design  of  large 
reservoirs  under  any  predetermined  conditions  where  the  land 
has  a  given  slope.  In  an  individual  case,  it  may  be  easier  to  use 
the  cut-and-try  method.  For  example,  assume  the  reservoir 
diameter.  Calculate  the  corresponding  depth  for  the  given  capac- 
ity output,  and  to  this  add  the  seepage  and  evaporation  losses 
during  the  irrigation  season  less  the  wrater  supplied  to  the 
reservoir  in  that  period  =  g  —  k,  and  to  that  add  the  clearance. 
Then  the  depth  being  determined,  calculate  the  volume  and  cost 
of  embankment,  cost  of  lining,  cost  of  land,  and  cost  of  riprap. 
Figure  the  annual  cost  and  the  total  fixed  charges,  cost  of  lost 
water,  and  hence  the  storage  charges  on  the  water.  Then  assume 
nt'w  diameters  and  repeat  calculations  until  the  minimum  cost  is 
reached. 

In  the  figures  to  follow,  the  cost  of  clearing  and  grubbing,  if 
necessary,  must  be  included  in  the  cost  of  land,  but  in  many 
places  where  labor  is  very  cheap,  sufficient  wood  may  be  obtained 

219 


220  PRACTICAL  IRRIGATION. 

to  help  pay  for  costs  of  this  nature.  No  expense  is  figured  for 
removing  surface  soil  under  embankments,  nor  for  trenching  if 
necessary,  for  a  puddle  core.  Such  cost  should  add  to  the  term 
F,  to  follow  a  quantity  2  tip  Z,  where  Z  =  the  additional  cost  of 
all  such  work  per  foot  length  of  embankment. 

Economic  Design  of  Large  Reservoirs  on  Level  Ground. 

The    following    figures    will    apply    approximately    to    large 
reservoirs  :  * 

Cost  of  embankment  =  (W  +  TH)     ™_ 
Cost  of  riprap  =  2  xrSm(H  —  q). 

TCTf^V 

=  43560- 

The  cost  of  reservoir  will  be  the  sum  of  these  three  quantities. 
Annual  fixed  charges  on  reservoir 


(1) 


Annual  cost  of  water  furnished  to  reservoir 


Annual  water  output  from  reservoir  in  acre-feet 


Hence  H  -  .+  B  ......     (4) 

' 

Total  annual  cost  =  D  =  Fixed  charges  +  cost  of  water  fur- 
nished to  reservoir  =  (1)  +  (2). 

*  These  symbols  are  given  on  page  204. 


APPENDIX   B.  221 

Substituting  the  value  of  H  found  in  equation  (4),  in  the 
expression  for  D,  differentiating  the  same  with  respect  to  r, 
and  equating  the  result  to  zero,  we  derive  an  equation  with 
A  and  r  as  variables,  which  'gives  the  radius  of  the  reservoir 
constructed  according  to  the  principles  laid  down,  i.e.,  for  a 
minimum  annual  cost  for  a  given  output  capacity,  A. 

Omitting  mathematical  details,  the  following  results  are 
obtained  : 

A  =  [\/4  FI  +  G2  +  4  Mr  -  G\  £j   ......     (5) 

D      rF      G       IA       Jr* 

E  =  -7  =  —r-  +  -  -  +  r—  g  +47-7  +  Z  =  Cost  per  acre-foot  output. 
A        A         T        o  /        2i  A  /n\ 

\Yhere  F,  G,  I,  and  J  are  constants  having  the  following  values: 

F  =  ^^  (WB  +  B2T)  +  Smp  (B  -  q)  2  TT 

£t  ' 

=  .2325  B  (W  H-  BT)  pn  +  6.283  mp  (B  -  q)  S: 


7  =  ^          -2  pnT  =  134,300,000  pnT 


In  equation  (6),  the  first  three  terms  relate  to  fixed  charges 
on  the  cost  of  the  reservoir  construction;  the  term  containing 
J  relates  to  the  cost  of  lost  water  and  interest  on  land  invest- 
ment, and  the  last  term,  /,  is  the  cost  per  acre-foot  of  the  water 
supplied. 

Hence  the  cost  of  the  reservoir  construction  per  acre-foot 
output 

?      G     I 


222 


PRACTICAL  IRRIGATION. 


Then  the  following  are  values  of  the  constants  in  four  of  the 
cases  considered : 


Case 

la 

2a 

lb 

26. 

F 

3218 

2406 

3218 

2406 

G 

1879 

1329 

1879 

1329 

I   .  . 

3  355  000 

2  350  000 

3  355  000 

2  350  000 

J   .... 

000195 

000195 

00145 

00145 

4FI+G2.  .  .  . 
4IJ 

7,850,000 
2620 

4,030,000 
1835 

7,850,000 
19  560 

4,030,000 
13  700 

Let 

Then  in  case  la 
R2 


A  =  —  L  [V7,850,000  +  262,000  R-  1879]: 


0.25. 


Economic  Design  of  Large  Reservoirs  on  Sloping  Ground. 

Let  the  slope  of  the  ground  =  a, 

Let  the  mean  height  of  the  embankment  =  H\ 

Then  the  cost  of  the  embankment 


-  (W  +  TH) 


27 


27 


Annual  fixed  charges  on  reservoir 


43560  ' 


Similarly  the  equation  corresponding  to  (5)  is 


iL 
21 


and 


(7) 


(8) 


r¥_     G      7A        Kr*      Jr*_ 

A  O   ^.3  *)     A  ct     A         '  ."         *         *         *         •          \*^/ 


APPENDIX  B.  223 

where  F,  G,  I,  J  have  the  same  values  as  in  the  previous  case, 
and  K 

It  is  to  be  noted  that  the  equations  found  in  this  case  apply 
strictly,  only  when  the  lowest  depth  of  embankment  is  somewhat 
in  excess  of  the  clearance;  also  that  while  the  surface  for  evapo- 
ration will  continually  diminish  when  the  higher  part  of  the  res- 
ervoir starts  to  go  dry.  Still  the  fact  that  part  of  the  water  is 
spread  out  in  a  thin  sheet  and  hence  subject  to  more  rapid  evapo- 
ration will  be  assumed  to  compensate  for  the  diminished  surface. 

Economic  Designs  of  Large  Reservoirs  on  Sloping  Ground,  for 
Fixed  Belt  of  Riprap,  t  Feet  in  Width. 

The  equation  corresponding  to  (7)  is  annual  fixed  charges 
on  the  reservoir 


Equations  (8)  and  (9)  still  hold  where  /,  J  and  K  have  the 
same  values  as  above,  but 

F  =  .2325  pn  (WB  +  B2T)  +  2tmpx, 
and  G  =  3228  (W  +  2  TB)  pn: 

I  =  134,300,000  pnT: 


K  =  .349  tfnpT. 

Lined    Reservoirs  Constructed  on  Sloping  Ground,  with  Fixed 
Width  of  Riprap. 

The  effect  of  a  lining  is  to  increase  the  cost  of  land  so  much  an 
acre,  and  all  equations  given  above  will  still  be  applicable,  with 
the  exception  that  the  term  for  J  becomes 

J  -  ^-  (ri  +  (B  -  C)  I  +  43560  top), 
where  w  =  cost  of  lining  per  square  foot. 


224  PRACTICAL  IRRIGATION. 

The  arithmetical  part  of  the  calculations  may  be  greatly 
simplified  in  the  following  manner.  First  calculate  F,  G,  I,  J,  K 
for  any  given  case.  Then  let 

G2  +  4  FI 

a  = 


b  = 


1,000,000 
4/J 


10,000' 
4IKf 

100  : 

G 


1000 
10,000,000 


H 


21  100 


4          , 

Then,  —  =  V  (a  +  bR  +  cR2  -  d)e. 

Make  the  following  form : 

R 

a 

bR.. 


Sum 

Square  root  of  Sum 
d 
Difference. 


A 

R 

A 

A^ 

R3 


AITEXDIX   B.  225 


10  d 


100  fl        R 
I A  A 


106  R3  X  3       '  R3 ' 
KR3  x  10*      ?JR3 

3   A  A 

iL  yi 

s  =  Sum. 
JR*  X  104       9R 
2A  A 

I. 
Sum  =  cost  per  acre-foot  output 


H-  1-386^ 

#  -  B 

Efficiency  =  — = 

n.   —  L> 

o 

Cost  per  acre-foot  capacity*  =  —.... 

If  lined,  cost  per  acre-foot  capacity 
O4  43560 


2  A          43560  wp  +  m  +  (B  -  C)  I     p 

It  will  be  easier  to  start  with  r  and  find  the  corresponding 
value  of  A  than  to  endeavor  to  solve  equation  (8)  for  r  when  A 
is  given,  though  the  former  is  a  cut-and-try  method. 

Economic  Design  of  Large  Lined  Reservoirs  of  a  Given 

Capacity  not  Riprapped,  Neglecting  the  Value 

of  the  Water  Lost  by  Evaporation. 

Here  equation  (8)  still  holds, 

but  F  =  .2325  pnB  (W  +  BT): 

G  =  3228  pn  (W  +  2TB): 
I  =  134,300,000  pnT: 

*  Unless  the  bottom  is  lined. 


226  PRACTICAL  IRRIGATION. 


K  - 

rF      G      IA      Jr2       Kr3 
and  *-_  +  -+_+_+_  +  j    .     .     .     (e) 

If  the  reservoir  is  to  be  built  for  the  cheapest  cost  per  acre-foot 
for  a  given  capacity,  then 

F  =  .2325  nB  (W  +  BT): 
G  =  3238  n(W  +  2  BT): 
I  ==  134,300,000  nT: 
_v  +  435GQwf 

6930 
K  =  M9a2nT: 

and  cost  per  acre-foot  reservoir  capacity 

rF      G     I  A      Jr2       Kr3 


If  in  the  above  the  actual  capacity  alone  be  considered 
without  reference  to  losses  of  water,  then  in  place  of  B  use  6. 

If  the  reservoir  be  of  small  diameter  these  figures  will  not 
hold,  but  approximate  results  may  be  figured  by  letting  r  be 
the  radius  of  the  center  of  the  embankment,  and  figuring  the 
cost  per  acre-foot  and  acre-feet  capacity.  Then  obtain  a  correc- 
tion factor  by  taking  ratio  of  real  capacity  to  figured  capacity, 
as  follows: 

(2r  -W-T(H+b) 
ratio  =  I  - 

V  2i  T 

To  obtain  the  true  cost  per  acre-foot,  divide  the  first  cost  per 
acre-foot  by  this  ratio.  To  obtain  true  capacity,  multiply 
first  capacity  by  this  ratio. 

To  be  accurate  this  correction  factor  should  be  applied  to  all 
cases  of  large  reservoirs  previously  considered. 

The  cut-and-try  method  will  usually  be  simpler  and  more 
accurate  than  this  method  for  any  individual  case.  To  apply 


MTKXDIX   K.  227 

this,  assume  various  depths  of  water  in  reservoir,  and  from  the 
table  or  curves  figure  various  diameters.  Then,  allowing  for 
clearance,  figure  from  tables  the  volume  and  cost  of  embank- 
ment. Also  calculate  cost  of  lining.  As  the  reservoir  increases 
in  depth,  as  a  rule  the  cost  of  embankment  will  increase,  and  the 
cost  of  land  and  lining  decrease.  When  the  sum  of  all  three 
costs  is  a  minimum  for  a  given  capacity,  the  reservoir  will  be 

cheapest. 

If  the  lining  be  carried  up  to  the  top  of  the  bank  on  the  inside, 

then 

Cost  of  earthwork  =  -^  n  (r  +  —  +  HTj  : 

Cost  of  land  =  -^  n  (r  +  W  +  2  TH?: 

43,560 


Cost  of  lining        =   wr.  [r<  +  2  H  (r  +  v    + 

(H  -  b)      f         T(H  -  6)T 

CaPacit^  -  TSjSn  *  \-r  +  —  T—  J  acre-feet- 

Economic  Design  of  Reservoirs  on  Level  Ground  for  the 
Storage  of  Artesian  Well  Water. 

I  '  =  Irrigation  Factor  of  well  without  reservoir. 
Acre-feet  output  of  well 

-L)   ....     (10) 


43,560  \1  -  U 
Acre-feet  used  in  Irrigation 

-  A.    (11) 


_  T 

43,560  L  1  -  U 

Whence, 

D  =  2  *pr[(W  +  TH)  ^  +  Sm  (H  -  q)] 


By  (11). 


228  PRACTICAL  IRRIGATION. 

(Wnz      z2Tn  z          ,    \ 

Hence,          D  =  2  npr  ( — —  +  ^-^  +  Sm-  -  qSm) 

*Zi  i  X         Zi  i  X^  X  I 

2  np  A  ft  znT      W n   t    0^  \  _  A2  2  nnpT 

"?  ~27^~ 


x    \  27  x        27 
GxpnT . 

J  = 
Then  equation  (13)  becomes 

Differentiate  with  respect  to  r,  and  equate  result  to  zero 
GA       IA2 


Hence,        A  =~[V4IF  +  G2  +4/Jr-G]     ....     (15) 

Fr      G       7A      Jr2 

and  E'  =  -  -  +  —  +  r-j  +  — .  +  Z. 

A        r       3r3      2^1 

In  the  above  formulse 


13,860  (1  -  t/)  x 

Cox's  Formula. 
/472  +  57-  2\  L 


1200 

where  H  =  friction  head  in  feet,  d  --=  diameter  of  pipe  in  inches, 
L  =  length  of  pipe  in  feet,  V  =  velocity  of  water  in  feet  per 
second. 


1  X  1)  E  X . 


Acre  feet,  11. 

Conversion  table,  17. 
Acre  inch,  11. 

Conversion  table,  18. 
Air  —  entrained  in  water,  137. 

Lift,  115,  116. 

Altitude,  —  effect  on  evaporation,  33. 
Application,  —  cost  of  water,  37,  39. 
Arid  zone  of  the  U.  S.,  1,  2. 
Artesian  wells. 

Cost,  190. 

Definition,  86. 

Reservoirs  for,  187  to  198,  227,  228. 

Flow  increase  by  pumping,  92. 

Static  head  of,   188. 
Artesian  well  water  cost,  189,  190. 
Automatic  cutout  for  pump,  134,  135. 

Basin  irrigation,  20. 
Bed  irrigation,  20,  22. 
Boiler  pumps,  cost  of,  118. 
Boiler  setting,  cost  of,  118. 
Boilers  —  Steam,  cost  of,  117. 

Cabbage  irrigated  and  non-irrigated,  9. 

Canal,  55,  56. 

Canal  linings,  55,  56. 

Canals,  method  of  laying  out,  56,  61. 

Canals  as  reservoirs,  48,  49. 

Velocity  of  water  in,  56. 
Capacity  of  earth  reservoirs  —  205  to  215. 

Calculation,  156  to  162,  219. 

Tables,  205  to  215. 
Centrifugal  pumps,  115,  116. 

Capacity  of,  119. 

Cost  of,  119. 
Charging  for  irrigation,  —  methods  of, 

141  to  146. 
Chezy  Formula,  60. 
Cippoletti  Weir,  67,  68,  69. 
Clearance  of  reservoirs,  154. 
Coal  tar  reservoir  lining,  78. 
Concrete  cores  for  dams,  73. 

Dam,  71. 

Lining,  cost  of,  78. 

Reinforce  pipe,  60. 
Conduits  for  watrr.  .55,  56,  57. 
Cone  reservoirs  capacity,  2(>r>  to  208. 
Contour  check  irrigation,  21,  '22. 


Contour  ditch  irrigation,  20. 

Core  for  dams,  73. 

Core  wall-puddle,  185. 

Cost  of  irrigation,  617. 

Crib  dams,  73. 

Crop  formation,  moisture  for,  4. 

Crop  returns  and  values,  37. 

Crops,  value  of,  9. 

Cubic  feet  conversion  table,  18. 

Cubic  feet  per  sec.  per  day  conversion 

table,  19. 
Cultivation,  deep,  advantages  of,  27. 

Effect  on  evaporation,  26,  30. 

Importance  of,  5. 

Uselessness  of  Poor,  30. 
Culverts,  59. 
Current  meter,  70. 

Dams,  construction  of,  70. 

Concrete  cores  for,  53. 

Curved,  72. 

Earth,  74. 

Failure  of,  72. 

Kinds  of,  71. 

Timber  crib,  73. 

Wooden,  73. 

Rock  fill,  73. 
Deep  well  pumps,  115. 
Depth  of  irrigation,  15,  16,  17,  35,  36,  37. 

Annual,  11,  12. 
Depth  per  irrigation,  12. 
Design  of  irrigation  plants,  12. 

Pumping  systems,  40. 
Ditches,  construction  of,  65. 

Flow  in,  65,  66,  67. 
Diversion  of  water,  Procedure,  42. 
Division  box,  65. 
Drainage,  importance  of,  6. 
Drops,   56,  57. 

Droughts,  effect  on  plants,  4. 
Duty  of  water,  11,  15,  16,  17,  34,  35,  36, 
37,  39,  172. 

At  Bakersfield,  138. 

Earth  dams,  74. 

Earth  embankments  for  carrying  water, 

58. 

Earth  reservoirs,  f'alrulation,  156. 
Capacity,  157  to  162. 


229 


230 


INDEX. 


Earth  tanks,  construction,   74,  75. 

Economy  in  design,  153. 

Importance  of,  153. 

Section  of,  153. 
Earthwork,  cost  of,  76. 
Economy  in  use  of  water,  6. 
Efficiency  of  reservoirs,    184,   185. 
Embankments,     reservoir,     calculation, 
156,  219. 

Construction,  74,    75,    180,    185. 

Curves  of,  159,  160,  163. 

Minimum  volume  of,   161,  217,  218. 

Section  of,  179,  180. 

Volumes  of  earth  in,  209  to  216. 
Engines,  gasoline,  cost  of,  117. 

Steam,  cost  of,  117. 

Steam,  efficiency  of,  117. 
Evaporation,  alkali  soil,  26. 

Annual  losses,  149. 

Capillarity  effect,  26. 

Color  effect  on,  26. 

Cultivation  effect  on,  26,  30. 

Deep  furrows  effect  on,  27,  31. 

Definition  of,  23. 

Efficiency,  effect  on,  23. 

Humidity,  effect  on,  24. 

Moist  soils  vs.  water  surfaces,  29. 

Mulches,  effect  on,  26,  31. 

Soil,  5,  30. 

Soil  moisture,  4. 
•     Sub-irrigation,  effect  on,  27,  32. 

Temperature,  effect  on,  24. 

Transpiration,  effect  on,  35. 

Water  and  earth  surfaces,  25. 

Water  surfaces,  altitude  effect  on,  33. 

Water   surfaces,    temperature,    effect 
on,  29. 

Wind,  effect  on,  24,  29. 

Flooding,  irrigation  by,  20. 
Flow  in  ditches,  65,  66,  67. 

in  porous  media,  52,  53'. 
Flumes,  57,  58. 

Rating,  69. 

Velocity  in,  58. 
Free  moisture  in  soils,  3. 
Frequency  of  irrigation,  12,  35,  36,  37. 
Friction  in  pipe-tables,  108  to  112. 
Fuel  consumption,  pump  plant,  122. 
Fuel,  Texas,  in,  123. 
Furrow,    deep,    effect    on    evaporation, 
27,  31. 

Irrigation,  20,  21,  22. 

Gallons,  conversion  table,  18. 

Gallons   per   min.    per   day   conversion 

table,  19. 
Gasoline  engines,  cost  of,  117. 

Plants,  fuel  consumption,  122. 

Pump  plants,  cost  of  Texas,  121. 


Gate,  head,  62,  63. 
Waste,  64. 
Sluice,  64. 

Head,    Losses   in   piping   entrance   and 

discharge,  107,  112. 
Velocity,  107. 

Heat,  methods  of  transference,  25. 
Heaters,  cost  of,  118. 
Hose  irrigation,  20. 
Humid  zone  of  the  U.  S.,  1,  2. 
Humidity,  evaporation,  effect  on,  24. 
Hydraulic  ram,  115,  117. 
Hygroscopic,  moisture  in  soils,  3. 

Inch,  miners,  70. 
Inverted  siphon,  57,  59. 
Irrigation,  charges  for,  141  to  146. 

Bakersfield,  128,  129. 

Cost  of,  6,  7,  39,  151. 

Cost  of  at  Bakersfield,  140. 

Definition,  3. 

Depth,  10,  11,  12,  15,  16,  17,  35,  36, 
37. 

Desirable  water  for,  9. 

Economic  limit  of,  147  to  152. 

Excessive,  10. 

Expense  of,  9. 

Irrigation    factor,    Artesian    well,    149, 
189,  190,  192. 

At  Bakersfield,  140. 

Definition,  13. 

Effect  on  cost,  124. 

in  Texas,  36. 
Irrigation,   Frequency  of,    10. 

Limit  of  in  Arid  America,  147. 

Meadow,  7. 

Methods,  20. 

Need  of,  2. 

Plant  design,  125,  126,  127. 

Practice,  34,  35,  36,  37,  39. 

Truck,  7. 

Value  of,  2,  6,  7,  8,  38,  40,  41. 

Value  of,  comparative  results,  8,  9. 

Value  of  —  dependent  on  climate,  7. 

Kern  County  Land  Co.,  129. 
Kern  River  Canal  Co.,  129. 
Kutter's  formula,  66. 

Lift-pump,  105,  106. 

Limit  of  irrigation  in  Arid  America,  147. 
Linings,  Reservoir,  78. 
Loss  of  head  in  entrance  and  discharge 
pipes,  107,  112. 

Masonry  dams,  71. 

Meadow  irrigation,  7. 

Measurements  of  water,  67,  68,  69,  70. 

Miners  inch,  11,  70. 

Minimum  volumes  of  embankment,  161. 


INDEX. 


231 


Moist  soils,  evaporation  from,  29. 
Moisture,  contents  of  saturated  air,  23. 
essive,  6. 

Free,  3. 

Hygroscopic,  3. 

To  moisten  soil,  5. 

Plant  requirements,  3,  4. 

Sensitiveness  of  crop  to,  7. 

Soil  disposition,  4. 
Motors,   poly-phase,   cost  of,   119. 
Mulches,  effect  on,  evaporation,  26,  31. 

Onions,  irrigated   and   unirrigated,  8. 
Open   bottom   wells,   79. 
Operation,  pump  plants  at   Bakersfield, 
137. 
mi  Pump  Plants,  cost  of,  122. 

Pipe  for  float  cut  outs,  135. 

Friction  in,  tables,  108  to  112. 

Redwood,  cost  of,  59. 

Reinforced  concrete,  60. 

Wooden,  cost,  60. 

Depreciation,  60. 

Capacity,  60. 

Pit-pump  at  Bakersfield,  132,  133. 
Plants,  growth  of,  4. 
Plant  growth,  moisture  for,  3,  4. 
Porous  media,  Flow  of  water  in,  52,  53. 
Power,  choice  of  for  pumping,  113,  114. 

Plunger  pumps,  115. 

for  pumping,  103,  104,  105. 
Pulsometers,  115,  116. 
Pump  efficiency,  103. 

Frames,  vertical,   130. 

Installation  at  Bakersfield,  130,  131. 

Lift,  105,  106. 

Plant  calculation,    125,   126,    127. 

Plant  operation,   cost   of,    1-2. 
Pump  plants,  cost  of  in  Texas,  121. 

Fuel  consumption,   122. 

Operation  of,  at   Bakersfield,  137. 

Reservoirs  for,    199,   202. 

Test  of,   at   New  Orleans,    124,    125. 
Pump  stations,  cost  of,  118. 
_-n  of,  113. 

Performance  at  Bakersfu-ld,  138,  139, 

140. 

Pump  tests,  106,  107. 
Pump  Water,  cost  of,  38. 
Pumping  Water,  cost  analysis,  119,  120, 
121. 

Method  of  charging  for,  142,  143,  145. 
Pumping,   cost  of  at   Bakersfield,   138, 
139,    140. 

Engines,  115. 

for  irrigation,  increase  of,  113. 

Power  for,  113,  114. 
Pumps,  air  lift,  115,  116. 

Boiler,  cost  of,  118. 

Centrifugal,  115,  116,  119. 


Pumps  —  Continued 

Deep  well,  115. 

Direct  acting  steam,  115. 

Hydraulic  ram,  115,  117. 

Power  for,  103,  104,  105. 

Power  plunger,  115. 

Pulsometer,  115,  116. 

Pumping  engines,  115. 
Puddle,  75. 

Lining,  cost  of,  78. 

Ram  Hydraulic,  115, 117. 
Rate  of  flow,  11. 
Rating  flume,  69. 
Reclamation  service,  43. 
Redwood  pipe,  cost  of,  59. 
Reservoir,  clearance,  154. 

Efficiency,  184,  185. 
Reservoir    embankments,  construction, 
77,180. 

Cost  of,  76,  77,  78. 

Section,  179,  180. 

Composition  of,  78. 
Reservoir  location,  value  of,  45,  46. 

for  pump  plant,  199,  202. 

Water,  cost  of,  45. 
Reservoirs,  advantages  of,   150,  152. 

American,  181,  182. 

Artificial,  74. 

Reservoirs,  artificial,  advantages  of,  47, 
48. 

Artesian  well,  187  to  198. 

Artesian  well,  assumed  cases,  191, 192. 

Artesian  well,  design,  191  to  198. 

Capacity  of,  205  to  208,  219. 

Capacity    and   volumes   of   Embank- 
ment, 209  to  215. 

Cases   assumed,    155,    168,    169,    172, 
173,   174,   203,   204. 

Correction  factor  for,  226. 

Design  of,   169   to   171;   174   to    IT'.i; 
220  to  228. 

Embankment  construction,  185. 

Embankment  volumes,  216,  219. 

Field  for,    166. 

Function  of,  46,  47,  48. 

Economic  use  of,  199  to  202. 

Large;  capacity  of,  162. 

Lined,  173,  174. 

Minimum  embankment,   217,   218. 

Notation,  155,  167,  203,  204. 

Sloping  ground,  172. 
Reservoirs,    contrasted,    artificial     and 
natural,  183,  184. 

Natural  and  artificial,  43. 

Natural,  construction  of,  70. 

Natural,  considerations  for,  44. 

Risk  of  damage  to,  185. 

Small,  advantages  of,  40,  41. 
Rock  fill  dams,  73. 


232 


INDEX. 


Salts,  rise  of  in  soil,  5,  6. 

Sand  trap,  64. 

Saturation,  moisture  of  air,  23. 

Soil,  3. 

Semi-arid  Zone  of  the  U.  S.,  1,  2. 
Sluice  gate,  64. 
Soils,  deep,  storage  of  water  in,  5. 

Moisture  disposition,  4. 

Saturation,  3. 

Void  space,  3. 

Specific  capacity  of  wells,  97. 
Spillway,  70,  71. 
Sprinkler  irrigation,  20,  21. 
Steam  engines,  cost,  117. 

Efficiency,  117. 
Steam  plants,  118. 

Fuel  consumption,  122. 
Steam  pumps,  direct  acting,  115. 
Steam  pump  plants,  cost  of,  121. 

Cost  of  operation,  122. 
Stevensons  formula,  155. 
Storage  in  soils,  Heavy  irrigations,  13. 
Storage  of  water,  cost  of,  45. 
Stored  water,  method  of  charging  for, 

144,  145. 

Strainers  for  wells,  79,  80,  81. 
Streams,  flow  of  as  supply,  42,  43. 
Subirrigation,    effect    on    evaporation, 
27,  32. 

Surface  irrigation  evaporation,  32. 
Suppressed  weirs,  67,  68,  69. 

Tablet  irrigation,  20,  22. 

Tanks,  earth,  74,  75,  199  to  202. 

Temperature  air,  28. 

Evaporation,  24,  29. 

Soil,  28. 

Water,  28. 

Tests,  pump,  106,  107. 
Timber  crib  dams,  73. 
Time  element  automatic  cut  out,  135. 
Transformer  house,  134. 
Transpiration  loss,  light  —  effect  on,  4,  5. 

of  crops.  35. 
Truck  irrigation,  value  of,  41. 

Underground  supply,   49,   50,   51,   129. 

Water  flow,  51. 
Unsuppressed  weir,  67,  68,  69. 

Value  of  crops,  37. 

Irrigation,  6,  7. 
Velocity  canal,  56. 

Flume,  58. 

Head,  107. 

Inverted  siphon,  59. 
Void  space,  soil,  3. 

Waste  gate,  64. 
Wave  height,   155. 

Water,  application,  cost  of,  20,  37,  39. 
Artesian,  cost  of,  189,  190. 


Water  —  Continued 

Conduction  and  distribution,  55. 

Duty  of,  11,  15,  16,  17,  34,  35,  36,  37, 
39,  138,  172. 

Economy,  6. 

Measurement,  67,  68,  69. 

Procedure  before  diverting,  42. 

Pumping  cost,  38,  119,  120,  121. 

Rights,  3,  42. 

Storage  in  deep  soils,5. 

Supply,  flow  of  streams,  42,  43. 

Surfaces,  evaporation  from,  29. 

Well,  cost  of,  100,  101, 
Weirs  at  Bakersfield,  133. 

Cippoletti,  67,  68,  69. 

Suppressed,  67,  68,  69. 

Unsuppressed,  67,  68,  69.        • 
Well  water,  air  entrained,  137. 

Cost  of,  100,  101. 

Cost  of  Artesian,   189,   190. 
Wells,  artesian,  86. 

Cost  of  in  Texas,  190. 

Flow  increase  by  pumping,  92. 

Reservoirs  for,  187  to  198,  227,  228. 

Reservoirs  with  assumed  cases,  191, 

192. 
Wells  at  Bakersfield,  132. 

Boring,  cost  of,  99,  100,  101. 

Casing  for,  100. 

Change  of  flow,  86,  87. 

Cleaning,    82. 

Calculation  of  flow,  91  to  96. 

Depression  of  water  in,  85. 

Draft  of  water,  82. 

Elevation  of  water  from,  82. 

Friction  in  entrance  to,  80. 

Hydrostatic  level,  85,  87,  93. 

Interference,   mutual,  85. 

Kinds  of,   98. 

Law  of  flow,  86,  88,  89,  90. 

Leakage  of  water  in,  87. 

Legislation  advisable,  100. 

Open  bottom,  79. 

Output  of,  at  Bakersfield,  140. 

Pumping  from,  83. 

Sinking,  79,  98,  99. 

Specific  capacity  of,   97. 

Strainers,  description,  81. 

Supply,  storage  of  ground,  97. 

Test  of  flow,  88,  89,  90.   ' 

Testing,   100. 

Water  level  fluctuation,  93,  94,  130. 

Water  strata,  82. 
Wild  flooding,  20. 

Wind,  effect  on  evaporation,  24,  29. 
Wooden  dams,  73. 
Zanjero,    142. 
Zones  of  the  U.  S.  Arid,  1. 

Humid,  1. 

Semi  Arid,  1. 


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